In today’s cloud-driven world, more users and organizations are shifting their email data from local clients to cloud platforms like Office 365. Among all email formats, EML is one of the most widely used. It stores single email messages and is supported by clients such as Thunderbird, Windows Live Mail, Apple Mail, eM Client, and other desktop-based applications. However, when users move to Office 365 for better accessibility, security, and collaboration, they often face a major challenge Office 365 does not support direct import of EML files. This makes EML to Office 365 migration slightly complicated without the right method.
This blog explains everything you need to know about how to Migrate EML to Office 365, including manual workarounds, automated methods, limitations, and best practices.
What Is an EML File and Why Move It to Office 365?
What is EML?
EML is a standard email file containing Text and HTML content, Sender & receiver details, Timestamps, Attachments, Metadata, Inline images
It’s saved as a single message, making it portable but harder to manage when you have hundreds or thousands of files.
Why Migrate EML to Office 365?
- Cloud Accessibility
Office 365 stores your mailbox on the cloud, allowing access from any device—desktop, mobile, or browser.
- Better Security
Office 365 includes multi-layer security features like MFA, DLP, ransomware protection, and compliance policies.
- No More Local Dependency
Unlike EML, which depends on the desktop app, Office 365 works anywhere with an internet connection.
- Easy Management & Organization
Office 365 organizes emails into folders, archives, and search tabs more efficiently than scattered EML files.
- Business-Level Features
Shared mailboxes, Teams integration, calendars, OneDrive, and enterprise tools make Office 365 a better choice for professionals.
Challenges in Converting EML to Office 365
- EML files cannot be imported directly into Office 365 because:
- Office 365 does not support uploading .eml files.
- EML belongs to older, desktop-based email clients.
- Formats are structured differently (single message vs cloud mailbox).
- Attachments and metadata may break if converted incorrectly.
Due to these limitations, we need proper methods to migrate EML data safely.
Methods to Migrate EML to Office 365
There are three primary methods.
Method 1: Import EML into Outlook and Then Sync to Office 365
This method works if you have Outlook installed on your computer.
Steps to export EML to Office 365:
Step 1: Drag & Drop EML into Outlook
Step 2: Sync Outlook with Office 365
If your Office 365 account is already added in Outlook:
- Select the imported EML folder.
- Drag and drop it into your Office 365 mailbox folder.
- Wait for Outlook to sync the data with the cloud account.
Pros:
- Free method
- Works for small quantities
- No technical expertise needed
Cons:
- Time-consuming for large EML collections
- May break attachments
- Drag-and-drop doesn’t always work
- Requires Outlook installation
- Best for personal use, not for corporate migrations.
Method 2: Use IMAP Migration
This method manually syncs EML files to an IMAP account, which then syncs to Office 365.
Steps to Migrate EML to Office 365 Using IMAP:
Step 1: Create an IMAP email account.
Step 2: Configure the IMAP account in a desktop client.
Step 3: Import EML files into the IMAP account’s inbox or custom folders.
Step 4: Add the same IMAP account to Office 365 and let it sync.
Pros:
- Works across devices
- Suitable for small-to-medium email volumes
- Free
Cons:
- Slow migration
- Chances of sync failure
- Attachments may be lost
- Folder hierarchy may break
- Use this if you don’t mind the long process and have time for syncing.
Method 3: Automated EML to Office 365 Migration Tool
The most reliable and efficient method is using the CubexSoft EML to Office 365 migration tool. This tool directly upload EML files into Office 365 mailboxes without requiring Outlook or IMAP. Also preserve your actual data format and the folder hierarchy. Also it has a very impressive and uncomplicated GUI to help even the users without even any advance technical knowledge. It supports conversion into multiple file formats like MBOX, PST, PDF, Office 365, Gmail, and many other file formats. Try the demo mode it lets you convert up to 25 emails instantly without any charges.
Benefits of Using Automated Tools:
- Bulk Upload Support
Whether you have 10 EML files or 10,000, tools handle everything at once.
- Perfect Formatting Preservation
HTML structure, inline images, signatures, metadata, CC/BCC everything stays intact.
- Complete Attachment Handling
No broken or missing attachments.
- Folder Structure Maintenance
Import your EML files into the same hierarchy you created.
- No Outlook Required
Great for Mac users who don’t want to install Outlook.
- Direct Upload to Office 365
Choose the mailbox and folders easily.
- Secure Migration
Tools follow modern encryption and authentication standards (OAuth, Modern Login).
- Fast Migration Speed
Cloud-to-cloud upload is much faster than IMAP.
If accuracy, speed, and security matter this method is the best.
Steps to Migrate EML to Office 365 Instantly:
- Set up the application on your system.
- Pick the emails you required for conversion.
- View the emails in the built in preview window in export panel.
- Choose the format for your exported files, here select Office 365.
- Select the save location.
- Now click the Convert button to begin the migration.
Final Thoughts
Migrating EML to Office 365 is no longer a complex task once you understand the right method. Whether you’re moving from Thunderbird, Apple Mail, eM Client, or Windows Live Mail, all EML data can be successfully transferred to Office 365 using the right approach. While manual methods to Migrate EML to Office 365 work for small jobs, CubexSoft EML Converter tools provide unmatched speed, accuracy, and reliability especially when dealing with large volumes or business-critical emails. also you can check out up to 25 emails for free using its demo mode for free.