Provider · IMAP
IMAP mailbox migration
Every mail service and almost every hosting panel speaks IMAP, so a mailbox can be moved between any two servers without asking either of them for permission. You need four things per side: server address, port, login and password. Below is where to find them, when the port is 993 and when it is 143, and how to connect while the domain still points at the old host.
Where to find the settings
For your own server the values live in the hosting panel, under "Mail → client configuration". Enter the hostname rather than an IP: the certificate is checked against what you type, and certificates rarely cover an IP.
- Server
- imap.yourdomain or mail.yourdomain — the name in the certificate
- Port
- 993 for SSL/TLS, 143 for STARTTLS
- Username
- usually the full address, sometimes user@domain or user
- Password
- the mailbox password; large services need an app password
What breaks a migration here specifically
- The server address is nearly always in the hosting panel under "mail client configuration", or in the message the provider sent when the mailbox was created. With no panel, imap.yourdomain or mail.yourdomain usually answers.
- Port 993 means SSL/TLS, port 143 means STARTTLS. We never connect unencrypted and never turn certificate verification off: a certificate that fails validation shows up in the log instead of being silently ignored.
- While a domain is moving to a new provider, your own mail.yourdomain still resolves to the old host. The right workaround is not an IP but the hosting provider’s own mail hostname (something like mail.hoster.tld), which does not depend on your DNS: the certificate is verified against exactly the name you typed, and certificates are almost never issued for an IP.
- On some hosts the login is not the email address but user@domain or plain user. An authentication failure with a correct password usually means exactly this.
Where mailboxes go from here
Ready pages with the settings for both sides and the order of steps.
FAQ
Common questions
What if I do not know the IMAP server address?
Look for "Mail → client configuration" in the hosting panel. With no access, try imap.yourdomain and mail.yourdomain on port 993 — on most hosts one of the two answers.
Does the mail pass through your servers?
In the online mode messages stream from the source server to the destination server; we keep no copies. If handing over passwords is out of the question, the local client runs on your own machine with no infrastructure of ours involved.
Can I enter an IP instead of a hostname?
The field accepts one, but the connection succeeds only if the server certificate covers that IP — which is rare. Verification runs against whatever you typed and cannot be turned off: skipping it is exactly how a password ends up on the wrong server. During a domain transfer use the hosting provider’s hostname instead of your own.
What about a self-signed certificate?
The connection is refused and the reason lands in the log. The right fix is a real certificate — Let’s Encrypt is free — not disabling verification.
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