Test the connection between the EXM and the MTA
Abstract
How to verify the connection between EXM and the MTA.
If you use the Sitecore Message Transfer Agent (MTA) or if you have configured a custom MTA server, you can verify the connection between the MTA and EXM.
To test the connection between EXM and the MTA:
In the Content Editor, select the Email root item.
On the Email tab, in the Server group, click Test Connection.
If the test is not successful, an error message appears with information to help you troubleshoot the problem.