Postfix weird behavior after transfer vhost to newer server, adding @com

[borjaevo]

SYSTEM INFORMATION
OS type and version Debian 10
Virtualmin version 7.1-1

I have migrated some virtual hosts to another server with very similar configuration. The old its a debian 9 and the new is debian 10, the rest is the same, same virtualmin, webmin and software servers versions.

I cannot receive new incoming email:

Aug 31 10:48:42 imatec-server postfix/smtp[13426]: 68EC6EA3189: to=user.domain@com, orig_to=user@domain.com, relay=none, delay=0.24, delays=0.21/0.02/0.01/0, dsn=5.4.4, status=bounced (Host or domain name not found. Name service error for name=com type=A: Host found but no data record of requested type)

I changed real address and domain for “user” and “domain”. As you can see, is adding @com to the mapping or something like that. Im comparing both servers postfix configuration. But i cant see where the problem is.

Thanks

[borjaevo]

The problem was on the option “What domain to use in outbound mail” of Postfix General Options. I have set the option “use domainname” that appears to be empty in all cases. So i changed to /etc/mailname witch is file that contains the hostname of the server. Now its resolving the address as user.domain@hostname.com
I really dont understand this way of mapping. I think with email accounts with address like “user@domain.com” its not translating to a user of the hostname.
I always had the problem of using TLS smtp certificate so i have to use a certificate for the hostname domain instead of the virtualhost domain and maybe is related to this.