unable to connect to the destination SMTP

[kucing]

I am using AMS 2012 and I configured it already. I can send/receive email from Gmail, Yahoo, Hotmail, etc. But there is problem with some domains that I cannot send/receive to. I checked all my mx record, reverse DNS, incoming and outgoing server with mxtools, everything are fine.

But why I still received bounce email username@domain.com from some domains and saying that my domain is “unable to connect to the destination SMTP”.

Please can you help me to check this problem.
thank you.

[Code Crafters]

This error means that the domain you're sending to didn't have valid mx / dns records pointing to a valid mail server. This isn't generally any issue with your setup. As long as outgoing mail test dns and test outgoing route buttons return no errors you should be setup fine.