Did you just get done setting up an Exchange 2013 server and everything seems to be working fine? Well, don’t break out the champagne yet if you haven’t changed the SMTP banner on your internet email Receive Connector! It’s easy to configure reverse DNS at your ISP and think you’re done getting mail flowing smoothly, but a quick check at MXToolbox, running their SMTP test on your domain will reveal that your server probably didn’t correctly configure the SMTP Banner. Sure, mail seems to be flowing fine in the first day or two after the initial set up, but inevitably someone will start complaining about a domain that they can’t send to for some reason. It’s not common, but there are domains who won’t accept email if the Banner doesn’t match your domain name. This relatively uncommon problem is why it’s so difficult to discover without a test like MXToolbox offers – especially since you won’t stumble across it in the GUI – it’s a command that must be entered using the Exchange Management Shell. (Ugh!)
Anyway, here’s what you need to enter in your administrator-level EMS, changing the relevant server & domain names to suit your situation:
set-receiveconnector –identity “SERVERNAME\Default Frontend SERVERNAME” –banner “220 mail.domain.com Microsoft ESMTP MAIL Service ready” -ConnectionTimeout 00:15:00
The change takes effect immediately (assuming EMS didn’t give you any error messages after you did it). You don’t need to restart any services or anything – you can just go back to MXToolbox and run another test, and you should now see the Banner looks good, and hopefully that takes care of the last flaw in your otherwise smoothly-running server. :)