DNS local zone

[freightcar]

thanks for the response.

i enabled query logging and found out that it queries for
monitor.company.com instead of monitor. the problem was that the
resolver (not MUA or MTA) adds local domain to hostname if no domain
name is present. so if sending to user at monitor the resolver will not
query monitor it will query monitor.company.com. and I had
monitor.company.com in /etc/hosts. and my hostname was pc.company.com
so when i ping monitor , the resolver will add company.com and it will
resolve. but even though there was a mx record for monitor, there was
no mx record for monitor.company.com so the email could not be sent.
the one solution for this is create a mx record for monitor.company.com
and let resolver do its job. the other solution is to change hostname
to non-fqdn so if the hostname was pc (in contrast to pc.company.com)
the root domain will be assumed by resolver, and it will query monitor,
for which mx was already created.