MessageSender: "Error: 550 not local host..."

[support]

If you are getting an "Error: 550 not local host...not a gateway" error, eg. "Error: 550 not local host xyzcompany.com not a gateway", with MessageSender then you will need to check a couple of things:

First of all, make sure that you are using the correct SMTP Authorization for the SMTP server you are connecting to.

Secondly, check that Message Sending/SMTP Sender Details/Email is set to the same email address as Connection/Message Sending/SMTP/Account Name. Some SMTP servers allow you to use other email addresses, while others require you to use the same email address for both settings.