While creating a mailing if an SMTP error occurs while sending a test email on "step 4" page a fatal error is triggered

Create a new mailing on "Test (step 4 of 5)" enter an email in the "Send to Address" and hit the "Send a Test Mailing" button. If anything is not correctly setup with the SMTP server then the fatal error template is shown:
"Sorry but we are not able to provide this at the moment.
Failed to add recipient: lola@freeform.ca [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: 550, response: Verification failed for No Such User Here" Sender verify failed)]"

It would be preferable to show this error message in the usual Civi error dialog rather than a fatal error screen.

Additional info for the error message besides the possible config of outgoing email: A common reason for problems with the test email is that the email server is not configured to support VERP.
(A search of the forums for "smtp.php" shows around 50 results for users needing to edit this file)