I am running CiviCRM 4.6.8 on Wordpress 4.3.1. I have configured my hosting providers SMTP details (as provided by them) under outbound email settings and when I click on "Save & Send Test Email", the email is sent successfully.
When I compose a new mailing under Mailing -> New Mailing, and click on the "Send Test" button to send a test email to myself, I get this error:
Error in call to Mailing_send_test : Failed to set sender: b.167.72.4a390771944bc4a6@ [SMTP: Invalid response code received from SMTP server while sending email. This is often caused by a misconfiguration in Outbound Email settings. Please verify the settings at Administer CiviCRM >> Global Settings >> Outbound Email (SMTP). (code: 501, response: : domain missing or malformed)]
What is the problem here and how do I resolve it?