- Plesk for Linux
One of the following errors showing when trying to to send emails via Horde / Roundcube mail client:
PLESK_INFO: Warning: There was an error sending your message: Error connecting to SMTP server.
PLESK_INFO: SMTP Error (-1): Connection to server failed
In Horde log
/var/log/psa-horde/psa-horde.log, the following error can be found:
CONFIG_TEXT: ERR: HORDE [imp] Error connecting to SMTP server.  Connection refused [pid 6716 on line 1160 of "/usr/share/psa-horde/imp/lib/Compose.php"]
- Postfix is used as mail service and it is in stopped status:
# service postfix status
Redirecting to /bin/systemctl status postfix.service
● postfix.service - Postfix Mail Transport Agent
Loaded: loaded (/usr/lib/systemd/system/postfix.service; enabled; vendor preset: disabled)
Active: inactive (dead)
server-hostname systemd: Failed to start Postfix Mail Transport Agent.
server-hostname systemd: Unit postfix.service entered failed state.
server-hostname systemd: postfix.service failed.
SMTP Server Postfix is not running and thus cannot process mails.
Log into Plesk > Tools & Settings > Services Management and start the service: