[PLUG] Sendmail is unable to send emails to users in same domain

[Amey Abhyankar]

Hello,

I am trying to configure sendmail on gitlab 13.x CE [on-prem
server/CentOS 7] to send emails to the LDAP based gitlab users.
[on-prem/traditional set-up]

Sendmail is able to send email to any domains except its own domain.

In logs, I am getting a message saying that the connection is refused
by domain abc.com & the private IP of Windows based DNS server.
The mailing solution for abc.com is taken from Google.
We checked for any email in the queue from gitlab at gitlab.abc.com but
no email in blacklist or spam section.

mail sender is gitlab at gitlab.abc.com
Reply to is noreply at gitlab.abc.com

I tried to add abc.com domain in access file as = Connect:abc.com   RELAY
Tried with more R&D but same issue.
Not helping.

Any ideas how to fix the issue.
I did a lot of Google.
Those solutions did not work.

Regards,
Amey.