Relaying Denied

Question(s)

• I tried to send mail to someone, but got a "relaying denied" message (with the numbers 553 and/or 5.7.1).
• I can send mail to other people, but not to this person.

Context

This answer applies if the mail error message resembles the examples shown here:

Error Example #1

 The original message was received at Mon, 12 Dec 2005 14:18:11 -0500 (EST) from OUTGOING-AUTH.MIT.EDU [18.7.22.103]
 
  ----- The following addresses had permanent fatal errors -----
 <jkibbee@reccousa.com>
  (reason: 553 sorry, relaying denied from your location [18.7.7.80] (#5.7.1))
 
  ----- Transcript of session follows -----
 ... while talking to mailstore1.secureserver.net.:
 >>> DATA
 <<< 553 sorry, relaying denied from your location [18.7.7.80] (#5.7.1)
 550 5.1.1 <jkibbee@reccousa.com>... User unknown

Error Example #2

 The original message was received at Thu, 2 Feb 2006 15:14:49 -0500 (EST) from OUTGOING-AUTH.MIT.EDU [18.7.22.103]
 
 ----- The following addresses had permanent fatal errors -----
 <steve@melleroptics.com>
 (reason: 553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1))
 
 ----- Transcript of session follows -----
 ... while talking to backup-mx.choiceone.net.:
 >>> DATA
 <<< 553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)
 550 5.1.1 <steve@melleroptics.com>... User unknown
 <<< 503 RCPT first (#5.5.1)

Solution

• This error usually indicates a problem with the mail configuration of the company or organization you are sending mail to.
• Typically, they have a primary mail server that exchanges mail with MIT, and they also have a secondary mail exchanger. The error happens when the secondary mail exchanger is misconfigured, and doesn't know that it is supposed to accept mail for the company.
• The solution is to telephone or fax the company or organization, and tell their computer administrators that their secondary mail exchanger is broken, and is not accepting mail.

Advanced

Advanced users can verify the situation, by looking up the mail exchange (MX) records of the company in question.

• On a Unix or Macintosh computer, you can look up the MX records of company example.com by running the command

  host -t mx example.com

• On a Windows computer, you can look up the MX records of company example.com by running the command

  nslookup -type=mx example.com

  The output of the MX lookup will show a number, and an internet domain name. The problem typically happens when the backup MX machine (the one with the higher number) forgets that it is supposed to accept mail for the primary domain.