Symptoms
This problem can affect mail servers that are configured to send mail directly, as specified in the Domain (Sending) properties. Messages sent to any AOL addresses never leave the Outgoing Queue, while newer messages are sent without problem. Mail delivery warnings are returned to the sender and ultimately, a mail delivery failure message is returned. In this case the error message can be something like:
The IP address you’re using to connect to AOL is either open to the
free relaying of e-mail, is serving as an open proxy, or is a dynamic
(residential) IP address. AOL cannot accept further e-mail
transactions from your server until either your server is closed to free
relaying/proxy, or your ISP removes your IP address from their list of
dynamic IP addresses. For additional information, please visit
http://postmaster.info.aol.com.
Note: This error may also be seen in the SMTPSND log file produced when SMTP/POP3 logging is enabled.
Resolution
Please check that you are not configured as an open relay. In the Administrator program click View, Summary and if such a warning is present then follow the links to resolve the issue. You will then need to go to the url listed in the AOL message (see above) and follow the steps required to get your server removed from their open relay database.
Configure an entry in the routing table (on the Settings menu) to route *@aol.com to the SMTP server address provided by your ISP. Now, outgoing messages to AOL accounts will be routed via your ISP, and outgoing messages to all other recipients will continue to be sent directly. Mail routed by your ISP should be accepted by AOL as a trusted sender. If you have problems relaying mail through your ISP then you will need to contact them to discuss this.
Note This problem is due to the anti spamming measures imposed by AOL and can affect all mail servers in this way. AOL will not receive messages sent by mail servers that are configured as an open relay or that use a dynamic IP address.