How can I find out the server and port of incoming mail if there is only an email address?

Question

Backup

The server is not publicly known, and only offers to forward incoming mail to them - it works as it should.
There is an archive of letters for all the years that used to be, and I want to import them.
There is a program that can send these letters to a remote mailbox via IMAP.
But I only have a dummy (possibly) e-mail (it looks like a mailbox, because if you click "reply" - it answers as it should).
The question is to understand the imap-server address and port with the help of some utility and such and such a mother. And the login is probably the login from the CRM itself.
I already wrote to technical support, looking for what else can be done.

Answer 1

check telnet with ohm or whatever is convenient
but if there is an alias or something else, then even if the IMAP exists and is not closed - there is little sense in
the IP of the server itself, you can search through DNS (dig )

Answer 2

Which server accepts mail for the nichego.net domain can be found in DNS by looking for the MX record for the nichego.net domain. What ports are open there - you can see through nmap - unless, of course, the SB is not watching there :) - otherwise something will arrive in response :)