I’m trying to migrate to mailcow from an existing mail server, and I’d like to minimize downtime as much as possible. I was hoping I could pre-configure the mailboxes in mailcow, and run the sync jobs to pull all of the users’ current messages ahead of time, and then simply make the DNS switch.
However, when I attempt to add any mailboxes for that domain, I get an error that the mailbox name is invalid. I have added the domain to mailcow and it is active, but the mx is still pointing to the existing mail server. I am assuming this is the reason for the failure? Is there any way to force add the mailbox and avoid the checks?