I am using https://www.howtoforge.com/tutorial/perfect-server-debian-jessie-nginx-bind-dovecot-ispconfig-3.1/ My current Debian version is 8.8 Email server works fine but for some reason I am not able to send mail using Roundcube. - SMTP Error: [550] 5.7.1 message content rejected. cat /var/log/roundcube/errors [16-Aug-2017 09:27:34 -0700]: <u2ab165r> SMTP Error: Failed to send data. [550] 5.7.1 message content rejected in /usr/share/roundcube/program/lib/Roundcube/rcube.php on line 1712 (POST /squirrelmail/?_task=mail&_unlock=loading1502900790769&_lang=en&_framed=1?_task=mail&_action=send)
