Sep 19, 2018

Email Relaying Denied

"Relaying" is when you send email to one mail server, expecting it to pass the email on to its intended recipient who resides on a different mail server (known as "non-local email").  A mail server will produce a "Relaying Denied" error when an unauthorized user attempts to send non-local email.

The server error comes in many forms.  Here are some of the most common ones:

550 Relaying denied
550 Relay not permitted
550 Relaying not allowed
550 5.7.1 Unable to Relay
550 5.7.1 <[email protected]>... Relaying denied
553 SMTP Relaying Denied
553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)
554 <[email protected]>: Relay access denied

Mail servers will not relay mail from just anyone.  Otherwise, spammers could flood the mail server, making it do their dirty work.  You must be authorized to use a mail server for relaying.  Unauthorized users will always receive the "Relaying Denied" error.