Mailbox Providers 101 – Part 3 AOL Mail

Mailbox Providers 101 – A five part series about the industry’s biggest email domains.


Here at SocketLabs we have customers ask us questions everyday about the big mailbox providers.  These providers run a significant percentage of the consumer inboxes and some also offer corporate and private domain mailbox solutions.  Through the years of delivering billions of messages to these organizations we’ve gain some great insight.  In the third part of this series we will review what we know of the twenty year old mailbox provider – AOL Mail.

You’ve Got Mail!  The iconic sounds of this big mailbox provider are not the only part of the platform that has evolved over the last twenty years.  AOL, especially recently, has gone through some major changes.  Here is what we know about AOL:

Similar to Yahoo! Mail, AOL Mail also is well known for message deferrals.  The deferral messages issued by AOL are well documented on the AOL postmaster website.  These temporary errors are issue with high frequency during the warm-up period for new dedicated IP addresses.  Here at SocketLabs we’ve seen more deferral errors from AOL than any other service provider.  New senders need to have some patience during the initial ramp-up period with AOL.

AOL does not use third party blacklist data beyond the Spamhaus PBL (Policy Block List) that we are aware of at this time.  AOL does maintain a very extensive internal URL blacklist which it uses to block messages.  Rejections at the SMTP gateway with a 554 HVU:B1 indicate an issue with a URL in the message content.

While AOL may issues many deferrals and temporary errors they are very good in providing data back to senders about their reputation.  AOL not only support Feedback Loop complaints, but also provide a IP reputation look-up tool on their postmaster website.  This allows for a basic inquiry as to a senders standing with AOL.  Not many mailbox providers offer this insight.

Along with error codes and reputation information, AOL does offer a support ticketing system on their postmaster website giving another advantage to the provider over the unknowns of a provider like GMail.  One of the support options is the ability to submit a whitelisting request with AOL.  We’ve found whitelisting approvals to be difficult to obtain with AOL, but for large volume senders it can increase inbox placement rates.  The deliverability of messages to AOL is not affected with a SenderScore Certification from Return Path.

In the past year AOL has joined other major mailbox providers in supporting DMARC, a new email authentication policy standard which is based on top of SPF and DKIM authentication.  Both authentication technologies are automatically provided to SocketLabs customers which greatly helps improve inbox placement rates.

Stay tuned for Part 4 of our series on Mailbox Providers 101 when we discuss Microsoft Hotmail/!