{"id":11002,"date":"2026-06-18T08:58:23","date_gmt":"2026-06-18T08:58:23","guid":{"rendered":"https:\/\/www.sysinfotools.com\/blog\/?p=11002"},"modified":"2026-06-18T08:58:24","modified_gmt":"2026-06-18T08:58:24","slug":"import-ost-file-to-office-365","status":"publish","type":"post","link":"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/","title":{"rendered":"Import OST Data to Office 365 with Attachments in 2026"},"content":{"rendered":"<div class=\"p-4 mb-4\" style=\"border: 2px solid #005EFF; border-radius: 30px;\">\n<p><span style=\"font-weight: 400;\">&#8220;Our company\u2019s Exchange server is no longer available, and I need to import OST file to Office 365 without access to the original mailbox. The OST file contains thousands of important emails, but manual methods are causing sync errors. What is the most reliable way to migrate the OST data to my Office 365 account?&#8221;\u00a0<\/span><\/p>\n<p style=\"text-align: right;\"><strong>~ Santiago Gomez, Mexico<\/strong><\/p>\n<\/div>\n<div class=\"block_sum\">\n<p>Professionals managing critical email data encounter accessibility challenges when an Exchange server becomes permanently unavailable. In such scenarios, locally stored OST files remain readable but cannot be imported directly. The process to import OST offline files into Office 365 requires either a manual conversion approach or a professional utility for reliable data extraction. The <strong>SysInfo <\/strong> <a href=\"https:\/\/www.sysinfotools.com\/ost-to-pst-converter.php\" target=\"_blank\" rel=\"noopener\"><strong>OST Converter Pro<\/strong><\/a> provides a direct conversion path and migrates it into Office 365 without any data loss. This guide covers all available methods to help users execute a complete and error-free OST to Office 365 migration.<\/p>\n<div class=\"blog-btn\">\n<ul id=\"db-btn-container\" class=\"nav nav-tabs mt-4\" role=\"tablist\">\n<li class=\"nav-item\"><a id=\"windows-tab\" class=\"nav-link active\" role=\"tab\" href=\"#windows\" data-toggle=\"tab\" aria-controls=\"windows\" aria-selected=\"true\"><i class=\"icon-windows\"><\/i> Windows<\/a><\/li>\n<li class=\"nav-item\"><a id=\"mac-tab\" class=\"nav-link\" role=\"tab\" href=\"#mac\" data-toggle=\"tab\" aria-controls=\"mac\" aria-selected=\"false\"><i class=\"icon-apple\"><\/i> Mac<\/a><\/li>\n<\/ul>\n<div id=\"db-btn-containerContent\" class=\"tab-content my-2\">\n<div id=\"windows\" class=\"tab-pane fade active show\" role=\"tabpanel\" aria-labelledby=\"windows-tab\"><a class=\"sum-d-btn\" href=\"https:\/\/www.sysinfotools.com\/demo-version\/SysInfoTools-OST-to-PST-Converter-Demo.exe\"><i class=\"icon-windows\"><\/i> Download<\/a> <a class=\"sum-b-btn\" href=\"https:\/\/www.sysinfotools.com\/buynow\/ost-to-pst-converter.php\" target=\"_blank\" rel=\"noopener\"><i class=\"icon icon-basket\"><\/i> Buy Now<\/a><\/div>\n<div id=\"mac\" class=\"tab-pane fade\" role=\"tabpanel\" aria-labelledby=\"mac-tab\"><a class=\"sum-d-btn\" href=\"https:\/\/www.sysinfotools.com\/demo-version\/Sysinfo-Mac-OST-to-PST-for-Mac.dmg\"><i class=\"icon-apple\"><\/i> Download<\/a> <a class=\"sum-b-btn\" href=\"https:\/\/www.sysinfotools.com\/mac\/ost-to-pst-converter\/buy.php\" target=\"_blank\" rel=\"noopener\"><i class=\"icon icon-basket\"><\/i> Buy Now<\/a><\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_81 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<div class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/div>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#Why_Organizations_Should_Migrate_OST_File_to_Office_365\" >Why Organizations Should Migrate OST File to Office 365?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#Standard_Procedure_to_Import_OST_File_to_Office_365\" >Standard Procedure to Import OST File to Office 365<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#Why_Does_This_Method_Fall\" >Why Does This Method Fall?<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#Comparison_Between_the_Manual_and_Automated_Solution\" >Comparison Between the Manual and Automated Solution<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#End-to-End_Solution_to_Import_OST_File_to_Office_365\" >End-to-End Solution to Import OST File to Office 365<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#Exclusive_Features_of_SysInfo_OST_to_Office_365_Converter\" >Exclusive Features of SysInfo OST to Office 365 Converter<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#Steps_to_Import_OST_Offline_Files_into_Office_365\" >Steps to Import OST Offline Files into Office 365<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#Case_Study_Thornfield_Associates_Consulting_Seattle\" >Case Study: Thornfield &amp; Associates Consulting, Seattle\u00a0<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#End_Note\" >End Note<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"Why_Organizations_Should_Migrate_OST_File_to_Office_365\"><\/span>Why Organizations Should Migrate OST File to Office 365?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<ul>\n<li aria-level=\"1\">Access mailbox data from anywhere using a cloud-based platform.<\/li>\n<li aria-level=\"1\">Recover important emails stored in offline OST files.<\/li>\n<li aria-level=\"1\">Centralize business communication within a single environment.<\/li>\n<li aria-level=\"1\">Protect mailbox data with Microsoft&#8217;s advanced security features.<\/li>\n<li aria-level=\"1\">Eliminate dependency on old Exchange servers or Outlook profiles.<\/li>\n<li aria-level=\"1\">Simplify mailbox management through a centralized admin portal.<\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"Standard_Procedure_to_Import_OST_File_to_Office_365\"><\/span>Standard Procedure to Import OST File to Office 365<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Generally, there is no direct method to transfer OST files into Office 365. However, there is an indirect route that involves two steps. Follow the steps below:<\/p>\n<p><strong>Step 1: Convert OST to PST<\/strong><\/p>\n<ol>\n<li aria-level=\"1\">Firstly, make sure that your <strong>Exchange OST file<\/strong> is present in <strong>Outlook<\/strong>.<\/li>\n<li aria-level=\"1\">Then, go to <strong>File<\/strong>, and in the left side options, click on <strong>Open &amp; Export<\/strong>.<\/li>\n<li aria-level=\"1\">In the displayed options, select the <strong>Import\/Export<\/strong> icon.<\/li>\n<li aria-level=\"1\">Further, in the new dialog, select <strong>Export to a File<\/strong>. Click <strong>Next<\/strong>.<\/li>\n<li aria-level=\"1\">Pick for <strong>Outlook Data File (.pst)<\/strong> and again tap <strong>Next<\/strong>.<\/li>\n<li aria-level=\"1\">From the import folders list, <strong>select OST files\/folders<\/strong>. Hit <strong>Next<\/strong>.<\/li>\n<li aria-level=\"1\">After that, press <strong>Browse <\/strong>and search for a location to save the PST file.<\/li>\n<li aria-level=\"1\">Lastly, click the <strong>Finish <\/strong>button to convert the OST file to PST.<\/li>\n<\/ol>\n<p><strong>Step 2: Import OST to Office 365 After PST Conversion<\/strong><\/p>\n<ol>\n<li aria-level=\"1\">Start <strong>Office 365 Exchange Admin Center<\/strong> and choose <strong>Permissions<\/strong>.<\/li>\n<li aria-level=\"1\">Later, press on <strong>Organization Management &gt;&gt; + &gt;&gt; Mailbox Import Export<\/strong>.<\/li>\n<li aria-level=\"1\">Then, click <strong>Add &gt;&gt; Ok &gt;&gt; Mailbox Import Export &gt;&gt; Save<\/strong>.<\/li>\n<li aria-level=\"1\">Now, move back to <strong>Admin Center <\/strong>and press <strong>Setup &gt;&gt; Data Migration &gt;&gt; Upload File &gt;&gt; New Import Job<\/strong>.<\/li>\n<li aria-level=\"1\">In the dialog, enter the <strong>name <\/strong>and <strong>import description<\/strong>. Click <strong>Next<\/strong>.<\/li>\n<li aria-level=\"1\">Subsequently, enter the <strong>date <\/strong>and click <strong>Next<\/strong>. You will get a<strong> SAS URL. Copy it<\/strong>.<\/li>\n<li aria-level=\"1\">Next, download and run the <strong>Azure AzCopy Tool <\/strong>and provide the<strong> Network Path<\/strong> to import. Click <strong>Enter<\/strong>.<\/li>\n<li aria-level=\"1\">Once the PST file is uploaded, create a <strong>CSV <\/strong>to map the PST file with M365 accounts.<\/li>\n<li aria-level=\"1\">The <strong>Import window<\/strong> opens, select the options, and click <strong>Next<\/strong>.<\/li>\n<li aria-level=\"1\">At last, <strong>Select Mapping File &gt;&gt; Upload CSV &gt;&gt; Validate<\/strong> and click <strong>Save<\/strong>.<\/li>\n<\/ol>\n<table border=\"1\">\n<tbody>\n<tr>\n<td>\n<p>Note: Users who want to access their OST file in MBOX-supported platforms can check this guide to <a href=\"https:\/\/www.sysinfotools.com\/blog\/convert-ost-to-mbox\/\" target=\"_blank\" rel=\"noopener\"><strong>convert OST to MBOX<\/strong><\/a> in bulk.<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><span class=\"ez-toc-section\" id=\"Why_Does_This_Method_Fall\"><\/span>Why Does This Method Fall?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li aria-level=\"1\">The process is tiring and complex and needs technical expertise.<\/li>\n<li aria-level=\"1\">High data loss is possible with no recovery options.<\/li>\n<li aria-level=\"1\">Cannot bulk migrate OST files and complete mailbox data.<\/li>\n<li aria-level=\"1\">Requires a connection with the Exchange Server the whole time.<\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"Comparison_Between_the_Manual_and_Automated_Solution\"><\/span>Comparison Between the Manual and Automated Solution<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<table border=\"1\">\n<tbody>\n<tr>\n<td>\n<p><strong>Feature<\/strong><\/p>\n<\/td>\n<td>\n<p><strong>Manual OST to Office 365 Method<\/strong><\/p>\n<\/td>\n<td>\n<p><strong>SysInfo OST File Converter Pro<\/strong><\/p>\n<\/td>\n<\/tr>\n<tr>\n<td>\n<p>Migration Process<\/p>\n<\/td>\n<td>\n<p>Multi-step and complex<\/p>\n<\/td>\n<td>\n<p>Direct and simplified<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td>\n<p>Large OST File Handling<\/p>\n<\/td>\n<td>\n<p>Limited<\/p>\n<\/td>\n<td>\n<p>No file size restrictions<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td>\n<p>Data Loss Risk<\/p>\n<\/td>\n<td>\n<p>Higher<\/p>\n<\/td>\n<td>\n<p>Minimal<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td>\n<p>Selective Migration<\/p>\n<\/td>\n<td>\n<p>Limited<\/p>\n<\/td>\n<td>\n<p>Date Range Filter Available<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td>\n<p>Processing Speed<\/p>\n<\/td>\n<td>\n<p>Time-consuming<\/p>\n<\/td>\n<td>\n<p>Faster and automated<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td>\n<p>Success Rate for Enterprise Migrations<\/p>\n<\/td>\n<td>\n<p>Depends on configuration<\/p>\n<\/td>\n<td>\n<p>Designed for large-scale migrations<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2><span class=\"ez-toc-section\" id=\"End-to-End_Solution_to_Import_OST_File_to_Office_365\"><\/span>End-to-End Solution to Import OST File to Office 365<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><strong>SysInfo OST File Converter Pro<\/strong> gives IT professionals a straightforward way to export data from OST files without requiring any Exchange server access. Emails, contacts, calendars, tasks, &amp; journals are extracted and saved in multiple file formats. Enterprises handling large OST datasets can also use the tool to <a href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-to-google-workspace\/\" target=\"_blank\" rel=\"noopener\"><strong>import OST to Google Workspace<\/strong><\/a>. A Date Range Filter helps narrow down the extraction to specific time periods. Also, there is a technical support team available to solve your query 24*7.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Exclusive_Features_of_SysInfo_OST_to_Office_365_Converter\"><\/span>Exclusive Features of SysInfo OST to Office 365 Converter<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li aria-level=\"1\">Processes multiple OST files in a single operation.<\/li>\n<li aria-level=\"1\">Uses Date Range Filter for selective data conversion.<\/li>\n<li aria-level=\"1\">Previews mailbox data before starting the conversion.<\/li>\n<li aria-level=\"1\">Searches and exports specific emails or folders.<\/li>\n<li aria-level=\"1\">Help to <a href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-into-windows-live-mail\/\" target=\"_blank\" rel=\"noopener\"><strong>import OST file into Windows Live Mail<\/strong><\/a> and other clients.<\/li>\n<li aria-level=\"1\">Generates detailed conversion and processing reports.<\/li>\n<li aria-level=\"1\">Preserves folder hierarchy and email metadata.<\/li>\n<li aria-level=\"1\">Handles large OST files without size restrictions.<\/li>\n<li aria-level=\"1\">Compatible with all major Windows versions.<\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"Steps_to_Import_OST_Offline_Files_into_Office_365\"><\/span>Steps to Import OST Offline Files into Office 365<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ol>\n<li aria-level=\"1\">Download the <strong>OST Converter Pro Software<\/strong>.<br \/><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-22109\" src=\"https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/1.webp\" alt=\"Download the OST Converter Pro Software\" width=\"820\" height=\"437\" srcset=\"https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/1.webp 820w, https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/1-300x160.webp 300w, https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/1-768x409.webp 768w\" sizes=\"auto, (max-width: 820px) 100vw, 820px\" \/><\/li>\n<li aria-level=\"1\">Then, add your <strong>OST <\/strong>file or folders and click <strong>Proceed<\/strong>.<br \/><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-22110\" src=\"https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/2.webp\" alt=\"add your OST file or folders and click Proceed\" width=\"820\" height=\"437\" srcset=\"https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/2.webp 820w, https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/2-300x160.webp 300w, https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/2-768x409.webp 768w\" sizes=\"auto, (max-width: 820px) 100vw, 820px\" \/><\/li>\n<li aria-level=\"1\">Further, <strong>select <\/strong>and <strong>preview files <\/strong>to import and hit <strong>Proceed<\/strong>.<br \/><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-22111\" src=\"https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/3.webp\" alt=\"select and preview files to import and hit Proceed\" width=\"820\" height=\"437\" srcset=\"https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/3.webp 820w, https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/3-300x160.webp 300w, https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/3-768x409.webp 768w\" sizes=\"auto, (max-width: 820px) 100vw, 820px\" \/><\/li>\n<li aria-level=\"1\">After that, choose <strong>Microsoft 365 <\/strong>and <strong>sign in <\/strong>with its credentials.<br \/><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-22112\" src=\"https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/4.webp\" alt=\"choose Microsoft 365 and sign in with its credentials\" width=\"820\" height=\"437\" srcset=\"https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/4.webp 820w, https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/4-300x160.webp 300w, https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/4-768x409.webp 768w\" sizes=\"auto, (max-width: 820px) 100vw, 820px\" \/><\/li>\n<li aria-level=\"1\">Lastly, use <strong>migration filters <\/strong>and click <strong>Start Export<\/strong>.<br \/><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-22113\" src=\"https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/5.webp\" alt=\"use migration filters and click Start Export\" width=\"820\" height=\"437\" srcset=\"https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/5.webp 820w, https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/5-300x160.webp 300w, https:\/\/www.sysinfotools.com\/blog\/wp-content\/uploads\/2025\/02\/5-768x409.webp 768w\" sizes=\"auto, (max-width: 820px) 100vw, 820px\" \/><\/li>\n<\/ol>\n<div style=\"background: linear-gradient(135deg, #fafdff, #ddf2ff); border-left: 5px solid #1e4258; border-radius: 12px; padding: 20px 25px; margin: 15px 0px; box-shadow: rgba(0, 0, 0, 0.08) 0px 4px 14px; transition: 0.3s; font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; color: #2a2a2a;\">\n<h3><span class=\"ez-toc-section\" id=\"Case_Study_Thornfield_Associates_Consulting_Seattle\"><\/span>Case Study: Thornfield &amp; Associates Consulting, Seattle\u00a0<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Thornfield &amp; Associates Consulting, a <strong>60-person<\/strong> financial advisory firm in Seattle, lost access to all Exchange accounts within 48 hours after its parent company filed for bankruptcy. The IT team recovered <strong>60 OST files<\/strong> totaling 98 GB across multiple company laptops. Standard PST import attempts through Outlook generated over <strong>4,200 sync<\/strong> errors with no recoverable data visible in the new Office 365 profiles.<\/p>\n<p>The team deployed <strong>SysInfo OST File Converter Pro<\/strong> to process all 60 OST files directly into Office 365. Each file was loaded into the tool, previewed for accuracy, and exported to Office 365. Migration filters were applied to prioritize <strong>emails from 2020 to 2024<\/strong>. Over<strong> 112,000 emails<\/strong> were successfully imported into Office 365 within a very minimal time and with complete accuracy.<\/p>\n<\/div>\n<h3><span class=\"ez-toc-section\" id=\"End_Note\"><\/span>End Note<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>The SysInfo OST File Converter Pro provides a direct path to import an OST file to Office 365. The tool processes OST files of any size, preserves the complete folder hierarchy, &amp; delivers a verified migration with zero data loss. IT administrators managing multiple accounts can execute the entire process in bulk, reducing migration time significantly. For any enterprise or individual looking to import OST file to Office 365 after an Exchange server becomes unavailable, this utility remains a reliable and audit-ready solution.<\/p>\n<h4 class=\"faq_heading\">Frequently Asked Questions<\/h4>\n\n\n<div class=\"schema-faq wp-block-yoast-faq-block\"><div class=\"schema-faq-section\" id=\"faq-question-1781769299718\"><strong class=\"schema-faq-question\"><strong>Q1. What data can be migrated from an OST file to Office 365?<\/strong><\/strong> <p class=\"schema-faq-answer\"><strong>Ans:<\/strong> An OST file can contain emails, attachments, contacts, calendars, tasks, journals, and other mailbox items. These components can be migrated to Office 365 while maintaining the original folder structure.\u00a0<br><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1781769354915\"><strong class=\"schema-faq-question\"><strong>Q2. Can I import a large OST file into Office 365?<\/strong><\/strong> <p class=\"schema-faq-answer\">&#8211;<strong>Ans:<\/strong> Yes. Large OST files can be imported into Office 365, but manual methods often become slow and difficult to manage. The SysInfo OST File Converter Pro is designed to process large OST files without size limitations.\u00a0<br><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1781769372418\"><strong class=\"schema-faq-question\"><strong>Q3. How to import orphaned OST files to Office 365?<\/strong><\/strong> <p class=\"schema-faq-answer\"><strong>Ans:<\/strong> The SysInfo OST File Converter Pro can extract mailbox data from orphaned OST files and migrate emails, contacts, calendars, and other mailbox items directly to Office 365 without requiring access to the original Exchange server.\u00a0<br><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1781769390434\"><strong class=\"schema-faq-question\"><strong>Q4. Can I import archived OST mailbox data into Office 365?<\/strong><\/strong> <p class=\"schema-faq-answer\"><strong>Ans. <\/strong>Yes. Archived OST files can be imported into Office 365, provided the mailbox data can be accessed and exported. This helps organizations recover historical emails and preserve important business records.\u00a0<br><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1781769408434\"><strong class=\"schema-faq-question\"><strong>Q5. How can I skip similar OST files while importing OST files into Outlook 365?<\/strong><\/strong> <p class=\"schema-faq-answer\"><strong>Ans:<\/strong> If multiple OST files contain duplicate data, the SysInfo OST File Converter Pro allows users to filter and manage mailbox content before migration. This helps reduce unnecessary data processing and prevents duplicate mailbox items from being transferred.\u00a0<br><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1781769431674\"><strong class=\"schema-faq-question\"><strong>Q6. Will metadata be preserved after importing OST to Office 365?<\/strong><\/strong> <p class=\"schema-faq-answer\"><strong>Ans:<\/strong> Yes. A proper migration process preserves email properties such as sender information, recipients, subject lines, timestamps, attachments, and folder hierarchy, ensuring mailbox integrity after the import is completed.\u00a0<br><\/p> <\/div> <\/div>\n\n\n<div class=\"kk-star-ratings kksr-auto kksr-align-left kksr-valign-bottom\"\n    data-payload='{&quot;align&quot;:&quot;left&quot;,&quot;id&quot;:&quot;11002&quot;,&quot;slug&quot;:&quot;default&quot;,&quot;valign&quot;:&quot;bottom&quot;,&quot;ignore&quot;:&quot;&quot;,&quot;reference&quot;:&quot;auto&quot;,&quot;class&quot;:&quot;&quot;,&quot;count&quot;:&quot;14&quot;,&quot;legendonly&quot;:&quot;&quot;,&quot;readonly&quot;:&quot;&quot;,&quot;score&quot;:&quot;4.9&quot;,&quot;starsonly&quot;:&quot;&quot;,&quot;best&quot;:&quot;5&quot;,&quot;gap&quot;:&quot;5&quot;,&quot;greet&quot;:&quot;Rate this post&quot;,&quot;legend&quot;:&quot;4.9\\\/5 - (14 votes)&quot;,&quot;size&quot;:&quot;24&quot;,&quot;title&quot;:&quot;Import OST Data to Office 365 with Attachments in 2026&quot;,&quot;width&quot;:&quot;139.6&quot;,&quot;_legend&quot;:&quot;{score}\\\/{best} - ({count} {votes})&quot;,&quot;font_factor&quot;:&quot;1.25&quot;}'>\n            \n<div class=\"kksr-stars\">\n    \n<div class=\"kksr-stars-inactive\">\n            <div class=\"kksr-star\" data-star=\"1\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" data-star=\"2\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" data-star=\"3\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" data-star=\"4\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" data-star=\"5\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n    <\/div>\n    \n<div class=\"kksr-stars-active\" style=\"width: 139.6px;\">\n            <div class=\"kksr-star\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" style=\"padding-right: 5px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n    <\/div>\n<\/div>\n                \n\n<div class=\"kksr-legend\" style=\"font-size: 19.2px;\">\n            4.9\/5 - (14 votes)    <\/div>\n    <\/div>\n","protected":false},"excerpt":{"rendered":"<p>&#8220;Our company\u2019s Exchange server is no longer available, and I need to import OST file to Office 365 without access<a class=\"read-more ml-1 main-read-more\" href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/\">Read More<\/a><\/p>\n","protected":false},"author":1,"featured_media":22108,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[528],"tags":[],"class_list":["post-11002","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-mail-management"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.2 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Import OST File Data to Office 365 with Attachments in 2026<\/title>\n<meta name=\"description\" content=\"Discover the easiest ways to import OST files into Office 365 with all attachments intact. Secure OST to Microsoft 365 migration in 2026.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Import OST File Data to Office 365 with Attachments in 2026\" \/>\n<meta property=\"og:description\" content=\"Discover the easiest ways to import OST files into Office 365 with all attachments intact. 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These components can be migrated to Office 365 while maintaining the original folder structure.\u00a0<br>","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#faq-question-1781769354915","position":2,"url":"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#faq-question-1781769354915","name":"Q2. Can I import a large OST file into Office 365?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"-<strong>Ans:<\/strong> Yes. Large OST files can be imported into Office 365, but manual methods often become slow and difficult to manage. The SysInfo OST File Converter Pro is designed to process large OST files without size limitations.\u00a0<br>","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#faq-question-1781769372418","position":3,"url":"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#faq-question-1781769372418","name":"Q3. How to import orphaned OST files to Office 365?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"<strong>Ans:<\/strong> The SysInfo OST File Converter Pro can extract mailbox data from orphaned OST files and migrate emails, contacts, calendars, and other mailbox items directly to Office 365 without requiring access to the original Exchange server.\u00a0<br>","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#faq-question-1781769390434","position":4,"url":"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#faq-question-1781769390434","name":"Q4. Can I import archived OST mailbox data into Office 365?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"<strong>Ans. <\/strong>Yes. Archived OST files can be imported into Office 365, provided the mailbox data can be accessed and exported. 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This helps reduce unnecessary data processing and prevents duplicate mailbox items from being transferred.\u00a0<br>","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#faq-question-1781769431674","position":6,"url":"https:\/\/www.sysinfotools.com\/blog\/import-ost-file-to-office-365\/#faq-question-1781769431674","name":"Q6. Will metadata be preserved after importing OST to Office 365?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"<strong>Ans:<\/strong> Yes. 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