Change MX records after an email migration

Run the migration while mail still arrives at the old host. Nothing changes for anyone yet.

Change the MX records to the new host (your new provider lists them). DNS can take a few hours to update everywhere.

An hour or two later, press “Sync new mail again” on the progress page. Only messages that arrived since the first run are copied.

Run one more sync the next day if you like. It is safe to run as often as you want: duplicates are always skipped.

Update phones and mail apps to the new server.

Keep the old account for a week or two before closing it.

Check the report for messages that weren’t copied. The usual reason is a message larger than the new host accepts.