AOL mail seeing Yahoo deferrals as mail integration continues

170403180613-yahoo-aol-oath-780x439A few weeks ago we told you about AOL’s migration of their MX servers to Yahoo’s infrastructure as part of the merger of the two entities under Verizon’s new Oath brand. Since that change in early February, mail to AOL recipients has been handled by Yahoo’s servers. No specifics have been released on how the combined mail system will handle filtering, but observations of recent bounces may shed some light on that.

Over the past 2-3 weeks a number of senders have been seeing the dreaded “Yahoo deferrals” from recipients with AOL email addresses. These deferrals – temporary bounces usually caused by a high complaint rate – occur frequently for many high-volume senders mailing Yahoo recipients. These bounces are typically returned in a format similar to the following:

421 4.7.0 [XXXX] Messages from XX.XX.XX.XX temporarily deferred due to user complaints – X.X.X.X; see

The appearance of these types of bounces when sending to AOL recipients means you now have to contend not only with AOL’s spam filtering but with that of Yahoo. While AOL is known for its useful resources and responsive Postmaster team, the Yahoo Mail team can be more difficult to reach when issues arise. If you do run into any of these bounces, it’s probably a good idea to reach out to Yahoo via their Support form since the filtering is occurring on their mail servers.

– BG



  1. Great post! I regurlary have this issue on yahoo. We use to ask for delist, do there is any good practice to avoid this bounce? We don’t see any complaint on Yahoo (FBL tested and working well) . To try to avoid it we use to reduce volume, taking most active members but it doesn’t work well.



    • Sergio,
      Thanks for the comment. Yahoo complaints are not always reported, so even if the FBL shows a low number of complaints it still may be too many for Yahoo’s liking. Like most of the big providers, they may not return complaint data via the FBL if they see too many “bad” indicators from your IP or domain or if DKIM is unsigned or signed with a different domain.


      • Also, typically ESPs calculate complaint rate based on dividing the number of complaints by the number of emails delivered. Yahoo and other ISPs calculate this by dividing the number of complaints by the number of emails delivered to the INBOX, so the rate will be much higher on their end.


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