Take some time to check your mx records of your mailserver(s). You being an responsible systems manager know it’s fine but checking it would do you no harm. It could easily be that you have overlooked the fact that your smtp banner doesn’t match your reverse DNS entry for instance.
Al right then, how do we check it. Simple, this online website does it for you. Just fill in the domain name for the mx record you want to check and see what is happening.
We are looking for this:
Most times you will say an warning claiming your reverse DNS doesn’t match your SMTP banner. That can be easily fixed.
Reverse DNS does not match SMTP Banner
If you have an Postfix email server as we do, acting as an mailgateway, then all you have to do is edit the main.cf file, look for the section [myhostname] and change it to the value of the part [your ipaddress] resolves to [your domain]. Save the file and restart your postfix server.
There is also an check available to see if your mailserver is present in any blacklist.
Now go ahead and check yours: mxtoolbox
