Why am I receiving one of the following error messages:

521 5.2.1 :  AOL will not accept delivery of this message

521 5.2.1 :  Service unavailable. Please try again later.


The SMTP reply code 521 indicates an Internet mail host DOES NOT ACCEPT incoming mail. If you are receiving this error it indicates a configuration error on the part of the recipient organization, i.e. inbound e-mail traffic is being routed through a mail server which has been explicitly configured (intentionally or not) to NOT ACCEPT incoming e-mail.

To resolve this issue the recipient organization needs to resolve their infrastructure issues.

In large organizations, with many mail servers, this issue may be a transient error isolated to a particular mail host or cluster configuration (e.g. in a mail server failover situation.) If you are unable to contact the organization to have them resolve your issue, waiting a short time and resending may be all you need to do.

References: http://www.ietf.org/rfc/rfc1846.txt

Keywords: email, error, aol, service, smtp, infrastructure