I've been getting a lot of these errors for mail sent to Yahoo all of a
421 4.7.0 [TSS04] Messages from 184.108.40.206 temporarily deferred due to user
complaints - 220.127.116.11; see https://help.yahoo.com/kb/postmaster/SLN3434.html
(in reply to MAIL FROM command))
The included link states:
Error: "421 4.7.0 [XXX] Messages from x.x.x.x temporarily deferred due
to user complaints - 18.104.22.168" when sending email to Yahoo
This error indicates Yahoo is seeing unusual traffic from your IP
address and/or that emails from your mail server are generating
complaints from Yahoo Mail users.
I checked MXDomainTool and we're not on any blacklists (not that I would
expect that to be related). But I did a thorough check for any config
mishaps that might have us open relaying, but we are closed up tight.
However we do have virtual aliases on hosted domains that ultimately point
to yahoo.com addresses. Undoubtedly, I can reference instances of spam
received to the virtual and then forwarded on to Yahoo's mailserver from
But can they really blame the middleman (us) for mail that is just passing
through our hands? I mean, I understand it's possible for them to do
whatever they please. But mostly just looking for a sanity check that I am
corectly ascertaining what is happening and what they are doing?
I saw some earlier posts on a similar issue with Yahoo, but it related to
rate-limiting rather than 4-hour bans. Not sure if it was the same
instigating factor but they've just changed their policy...
Any ideas welcome... But also looking for a sanity check on one thing I
was thinking of trying:
Find any virtual aliases that point to yahoo.com or ymail.com addresses...
replace the aliases with a virtual MAILBOX that *forwards* to Yahoo. Then,
as per my configuration, any mail destinated for yahoo will be scanned by
Maia-Mailguard/SpamAssassin before it is allowed to leave for Yahoo.
My hope would be that once yahoo-destinated spam passing through my server
slows down they will unban.
TIA for sanity checks!