Moving your mail in

The thing that goes wrong in email migrations is not the copying. It is the second run, after the first one stopped halfway.

What you need

For each mailbox: the old server's IMAP address, the username, and a password. For Google and Microsoft, that means an app password rather than the account password, because both block plain IMAP sign-in by default. Generate one in their security settings.

Run it before you switch the MX

Create the mailboxes here, run the migration, then change the MX record. New mail keeps arriving at the old provider until the MX moves, so nothing is lost while the copy is running — and you can take as long as you need over it.

Running it twice is safe

Messages are matched by their own identifiers, not by position. A migration that was interrupted, or one you re-run the day after the MX switch to collect the last few messages, copies only what is missing. You will not end up with two of everything, which is the usual way this goes wrong.

What comes across

Folders, with their structure. Read and unread. Flags and stars. Attachments. Dates — the original dates, not the date of the copy, so your inbox is not suddenly all from today.

What does not

Provider-specific things that have no IMAP equivalent: Gmail labels on a message in more than one place become folders, filters do not transfer, and neither do calendar and contacts, which move separately. Be suspicious of any tool that claims otherwise.

How long

It depends on the other side far more than on us — most providers rate-limit IMAP hard. A large mailbox can take hours. The migration reports progress per mailbox and can be left alone.

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