- Plesk for Linux
The following error is shown upon an attempt to send an email via SquirrelMail:
Message not sent. Server replied:
Temporary authentication failure
454 4.7.1 firstname.lastname@example.org: Relay access denied
Relaying is not permitted for the localhost.
Note: if SquirrelMail is using an external SMTP server, the relay settings should be reviewed on the side of the corresponding SMTP server.
Log into Plesk and add localhost addresses to the mail server whitelist in Tools & Settings > Mail Server Settings > White List: