cPanel - SMTP Error (451): Failed to set sender


When you try to send mails from any email client using cPanel, you may see the following error flashed

SMTP Error (451): Failed to set sender ""  (Temporary local problem - please try later)


code 451 response temporary local problem please try later


Let you are trying to send mail from "" to ""

If "" is using local mail server, the command given below must display "" as result.

# cat /etc/localdomains | grep
If the output is null, add an entry for "" in /etc/localdomains.

Also remove the entry of "" in /etc/remotedomains if there exists one.