Prepare your IMAP source email system and get the information you need to migrate. The mailboxes have to exist in Microsoft 365 or Office 365 to use IMAP migration. These general steps apply whether you're migrating from Gmail or another IMAP system.įirst you have to create your users in Microsoft 365 or Office 365 and assign licenses to them.

The main steps you perform for an IMAP email migration are shown in the following illustration. You can distribute the new passwords after the migration if you want users to get to their old mailboxes. If users don't know the new passwords, they won't be able to get to their old mailboxes during or after the email migration. This lets you access the user mailboxes by using a new password that you know.

If you can't access user mailboxes, you'll have to reset the passwords. If you know the user passwords or can access their mailboxes by using administrator credentials, there won't be any impact to users until you shut down your source email system. To migrate email, you need access to the user mailboxes in your source email system. Common connection limits include client/server total connections, per-user connections, and IP address connections on either the server or the firewall. If you limited the connections to your source email system, it's a good idea to increase them to improve migration performance. The biggest email you can migrate is 35 MB. You can migrate a maximum of 500,000 items from a user's mailbox (emails are migrated from newest to oldest). This type of migration doesn't migrate contacts, calendar items, or tasks. You can only migrate items in a user's inbox or other mail folders. Therefore, before attempting any data migration to mailboxes, Microsoft strongly recommends keeping the automatic ELC disabling feature enabled, or manually disabling all MRM and archival policies. You can use the SkipAutomaticElcUpdate SkipMerging flag to keep ELC enabled during the migration, but doing so will result in the migration tool not searching for missing items to avoid this perceived data loss. The migration tool will also automatically re-enable MRM when the migration is Completed or Deleted. The result is perceived data loss rather than actual data loss, which makes it much harder to identify actual data loss during any content verification checks.Įffective from March 2024, to avoid flagging these items as missing, the migration tool will automatically disable MRM (also known as email lifecycle or ELC) for IMAP and Google migrations. Because of this, any messages that are deleted or moved to archive by these policies will result in the migration process flagging these items as 'missing'. Microsoft's data migration tool is currently unaware of tools enforcing messaging records management (MRM) or archival policies. Here are a few limitations to be aware of: If this option won't work for you, see Ways to migrate email to Microsoft 365 or Office 365 for other options.įor Windows PowerShell steps, see Use PowerShell to perform an IMAP migration to Microsoft 365 or Office 365.

Your source email system supports IMAP.

Use the Internet Message Access Protocol (IMAP) to migrate email when: You can migrate the contents of user mailboxes from your source email system to Microsoft 365 or Office 365.

Imap webmailer