Postfix mail server not working, how to fix it?

Question

linux

Good afternoon, I'm trying to create a mail server on a virtual machine to send messages over the local network. When trying to authorize through Thunderbird, an error pops up.
When you click the "Confirm Security Exception" button, the error pops up again. FQDN of the server.train.org server, but the mail client sees only mail.train.org
There is a lot of information on the Internet, but the error cannot be corrected. Thanks in advance.

Answer 1

postfix it accepts mail, and on your scripts you are trying to access mailboxes. not postfix is ​​responsible for this, but for example dovecot

Answer 2

make an alias,
but finally make the admin set everything up correctly