Which Path Fits Multiple Email Accounts?
Moving one mailbox is a copy task. Moving multiple email accounts needs a batch that maps every source account to a Microsoft 365 user.
| Path | Source | Moves | Use case |
|---|---|---|---|
| Microsoft IMAP batch | Any IMAP server | Mail only | Free route for a mail only move |
| Bulk IMAP tool | Any IMAP server | Mail, plus mailbox types on the vendor list | Shared and archive mailboxes |
| Cutover or hybrid | Exchange server | Mailboxes and contacts | Exchange on premises |
How does the Microsoft IMAP Batch Work?
Method #1: Microsoft IMAP Migration (Free)
Who it suits. Teams that move mail from an IMAP host to many users. Extra application. None.
Microsoft states that IMAP migration moves mail only. Contacts, calendars and tasks do not move.
The service copies up to 500,000 items per mailbox, newest first. The maximum message size is 35 MB.
- Create the Microsoft 365 users and assign licenses, because the target mailboxes must exist first.
- Prepare a CSV file with the source address and credentials for every mailbox.
- Create the migration endpoint for the IMAP server.
- Create a migration batch from the CSV file and start it.
- Update the MX record when the sync ends, then delete the batch.
Microsoft recommends the admin center wizard for fewer than 50 users. A CSV file is the easier route for more users. Disable messaging records management and archive policies on the target mailboxes before the batch starts, as Microsoft advises.
Which Tool Handles Shared and Archive Mailboxes?
Method #2: Bulk IMAP Migration Tool (Paid After Demo)
Who it suits. Admins who move multiple email accounts with shared mailboxes. Extra application. IMAP to Office 365 migration software.
The SysTools IMAP to Office 365 page lists bulk migration and CSV mapping for regular, archive and shared mailboxes. The demo handles 2 users. The vendor lists a 5 user license.
- Start the software and sign in to the Microsoft 365 tenant as an admin.
- Import the CSV file with the source and target accounts.
- Select the mailbox types and set the filters.
- Start the migration and review the report.
Check the vendor page for the current limits and the supported IMAP hosts before you buy.
What if the Accounts Sit on an Exchange Server?
Method #3: Cutover or Hybrid Migration (Free Wizard)
Who it suits. Organizations with Exchange on premises. Extra application. None.
An Exchange server moves with cutover for small teams and hybrid for large ones. Read the Exchange 2013 steps or the general Exchange to Exchange Online guide.
Where Else do Accounts Come From?
- Gmail accounts follow the Google Apps to Office 365 steps.
- Web hosting mailboxes follow the cPanel to Office 365 guide.
- Thunderbird profiles follow the Thunderbird to Office 365 guide.
- PST files follow the PST import guide.
Frequently Asked Questions
How do You Migrate Multiple Email Accounts to Office 365?
Create the users, prepare a CSV file with the source accounts and start a migration batch.
Does IMAP Migration Move Contacts and Calendars?
No. Microsoft states that IMAP carries mail only.
How Many Items does the IMAP Batch Copy?
Microsoft lists up to 500,000 items per mailbox, newest first.
What is the Maximum Message Size?
Microsoft lists a maximum of 35 MB per message.
Do the Mailboxes Need to Exist First?
Yes. The target mailboxes must exist and carry a license before the batch starts.
Which Route Suits More Than 50 Users?
Microsoft states that a CSV file is the easier route for more than 50 users.
Can Software Move Archive and Shared Mailboxes?
The vendor page lists regular, archive and shared mailboxes for its IMAP tool.
Author's Verdict
Use the Microsoft IMAP batch when mail is all you need to move.
Choose a tool for shared mailboxes, archives or extra reports.
Key Takeaways
- Create and license the target users first.
- Contacts and calendars need another route.
- A CSV file maps the source accounts.
Related Guides