SMTP settings are checked (with user@domain as login) and Track replies using VERP in Reply-To header is disabled (it worked before).
How come a generated email adress name is used as login, thus preventing CiviMAIL to send a test mail?
Drupal 7.61 CiviCRM 4.7.30
Jan 09 07:00:10 [info] Ignoring exception thrown by nullHandler:
10005, Failed to add recipient: user@domain
[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
This email address does not exist. Dit e-mail adres bestaat niet. Sender verify failed)]