Just a quick note to myself… A co-worker just notified me that they cannot send email using the web interface–squirrelmail.

squirrelmail Server replied: 553 sorry, that domain isn't in my list of allowed rcpthosts (#5.5.3 - chkuser)

This qmailrocks forum thread gives a quick workaround. Just set “SMTP AUTHENTICATION” to login as noted below.

<br /> /usr/share/squirrelmail/config/config.php<br /> $no_list_for_subscribe = false;<br /> $smtp_auth_mech = 'login';<br /> $imap_auth_mech = 'login';<br /> $use_imap_tls = false;<br />