AOL and Yahoo merge could impact your email delivery and MTA

A few weeks ago, AOL reported that AOL and Yahoo will come together under the OATH umbrella and merge with the Yahoo email infrastructure to serve both brands. This happened on 20 February 2018, and now all the AOL recipient domains’ MX, including the following, will point to
mx-aol.mail.gm0.yahoodns.net:

- aol.com
- verizon.net
- aol.co.uk
- aim.com
- netscape.net
- cs.com

Will your email delivery be affected?

Based on some quick reviews, Postmastery engineers saw that senders who had bad delivery to AOL will now see improved delivery if they had good delivery to Yahoo. Senders who had bad delivery to Yahoo and good to AOL, will probably experience the reverse.

Will your MTA be affected?

If your mail servers are operating in simple pass-through mode, and no static routes are defined to reroute AOL related domains to aol.com, then you need not make any changes in your MTA. You are all set!

If you are using static routes, then you do need to make changes. Below are some examples describing the configuration in PowerMTA.

domain-macro aol aol.com, aim.com, verizon.net, ..

<domain $aol>
  route aol.com
</domain>

This would still work for some domains, but not all AOL related domains, as some of these are still pointing to older MX servers.
The following rollup queue settings are now obsolete and should be removed.

<mx-rollup-list>
 mx mailin-01.mx.aol.com aol.rollup  
 mx mailin-02.mx.aol.com aol.rollup
 mx mailin-03.mx.aol.com aol.rollup
 mx mailin-04.mx.aol.com aol.rollup
  ..
<mx-rollup-list>

This should be replaced with the following:

<mx-rollup-list>
  mx mx-aol.mail.gm0.yahoodns.net yahoo-aol.rollup
  ..
<mx-rollup-list>

# Yahoo recommends 20 messages per connection.
<domain yahoo-aol.rollup>
  max-msg-per-connection 20
</domain>

Register FBL on both providers

FBL complaints would still come to mailboxes which are still on AOL infrastructure. As soon as the mailboxes are moved to Yahoo, the FBL reports will come from Yahoo. It is therefore strongly recommended to register FBL on both providers. Please be advised that Yahoo provides FBL reports based on DKIM signing domain, while AOL sends FBL reports based on sending IP addresses.