- Plesk Onyx for Linux
- Messages are not sent and stay in the server queue.
- Mailgun service is used for sending emails.
var/log/maillogthe following log can be found:
CONFIG_TEXT: (delivery temporarily suspended: SASL authentication failed; server smtp.mailgun.org[203.0.113.2] said: 535 5.7.0 Business Verification)
Server use Mailgun as relayhost and are being suspended for "business verification".
Issue is on Mailgun side. Contact Mailgun support to fix the issue.