Provider · Exchange Server
Exchange Server mailbox migration
On-premises Exchange always ships an IMAP service, but it is stopped by default — that is the first thing an administrator has to change. After that the mailbox behaves like any IMAP server and can move anywhere: to Microsoft 365, to Google Workspace, or to a mail server of your own. Below is what to start, what to check in the certificate, and where Exchange throttles.
Connection settings
The form fills these in for you as soon as you pick the provider.
- IMAP server
- mail.example.com
- Port
- 993 · SSL/TLS
- Username
- the full email address
- Password
- the mailbox password
What breaks a migration here specifically
- The "Microsoft Exchange IMAP4" service is not running by default. Start both halves — IMAP4 and IMAP4 Backend — and set them to automatic, or the connection drops right after the greeting.
- The certificate on the mail name must be real and must cover the exact name you type into the server field. A self-signed certificate is refused; there is no flag to work around it.
- The throttling policy caps concurrent IMAP connections per user. On large mailboxes that ceiling is far more noticeable than disk speed.
- Public folders are not reachable over IMAP: they are a separate Exchange store and move with Microsoft’s own tooling.
Where mailboxes go from here
Ready pages with the settings for both sides and the order of steps.
FAQ
Common questions
Which server address do I use for Exchange?
The external mail name — the one in the certificate, usually mail.yourdomain. With no external access, an internal name or IP works when the migration runs from the same network.
Is Exchange Online supported?
Yes, but it connects differently: outlook.office365.com with an app password. That is covered on the Microsoft 365 page.
Do users have to stop working during the migration?
No. The source is never modified and people keep working. A second run after the domain switch picks up whatever arrived while the move was in progress.
Are message dates preserved?
Yes — received dates and read flags travel with the messages, so folders in the new mailbox look like the old ones.
Find out how big your mailbox is. It costs nothing.
Connect two servers, look at the size and decide. Or take the client and keep everything on your side.
Code on GitHub · built on imapsync · no sign-up