Message not sent. Server replied:
Requested action aborted: error in processing
451 Temporary local problem – please try later
Solution:
1. Login into server using SSH
2. cd /usr/local/cpanel/base/3rdparty/squirrelmail/config/
3. vi config.php
in this configuration file search $useSendmail = false; and replace false to true
then restart exim
and courier-imap
/etc/init.d/exim restart
/etc/init.d/courier-imap restart