another admin configured the machine at 134.83.14.208 as a postfix email server, but users are complaining that the machine is only accepting incoming mail addressed to users @localhost.localdomain.

Identify one thing that could cause this issue. Describe how you could confirm you have found the cause (e.g. a command to run).

Describe how you would resolve this problem. For this step, you may assume you have identified and proved the correct cause of the problem