[Mailman-Users] understanding Yahoo's "email temporarily deferred due to user complaints"

Dave (FitEyes) dave at fiteyes.com
Thu Jun 7 19:37:04 CEST 2012

We received the following message from Yahoo. We want to understand what
happened and how to resolve it.

<somelistmember at yahoo.com>: delivery temporarily suspended: host
mta5.am0.yahoodns.net[] refused to talk to me: 421 4.7.0
[TS01] Messages from <OUR_IP_ADDRESS> temporarily deferred due to user
complaints -;
see http://postmaster.yahoo.com/421-ts01.html

The message has an attachment named noname.eml (as well as a details.txt
file). We are assuming this noname.eml is the triggering email (maybe the
one that was complained about). (BTW, it was not spam.)

This first response from Yahoo listed (in details.txt) 150 out of about 600
total Yahoo members on our list. These were the email addresses that we
could not send to for 4 hours. There were 4 subsequent similar messages
(each with a noname.eml attachment) from Yahoo (so 5 in total) and now this
affects 450 out of 600 Yahoo members on our list.

Among these five different noname.eml attachments, four were the exact same
message. So there were only two different emails. Both were from the same
author -- and the message is *not* spam.

It appears that only messages from this member are problematic (but our
sample size is small -- just 2 distinct messages -- and we're doing a lot
of guessing).

I don't see any problem with the triggering message, although the
attachment (noname.eml) has incomplete headers -- our usual DKIM signature
and SPF "pass" are missing. Apparently, the attachment includes only a
subset of the headers. I'm subscribed to the list and when I view this
email (the version I received directly from the list), the full headers
show a valid DKIM signature from our list, SPF pass, and all the other
expected headers. So it appears to me that there is nothing "wrong" with
the message that triggered this action.

It appears that Yahoo suspends emails to that server for four hours.


Their solution is to "wait for four hours". That doesn't seem to be enough
in this case, as this issue has continued for two days and is growing. We
want to resolve this properly (but we don't know what action to take).

Unfortunately, our understanding of this and attempts to resolve it are
complicated by the fact that there appears to be a 5 day delay. We have
gotten these notices for the last two days, but they apparently are
triggered by a message originating from our list 5 days prior to each

The member in question has sent about six more (non-spam) messages to our
list in the last few days, so we expect more of these messages from Yahoo
in coming days. Again, we don't know how to resolve this yet.

Our proposed course of action is:

   - since our list is completely moderated, we will hold all messages from
   this single "triggering" member (until we understand the problem).
   - temporarily *remove all our valid Yahoo members from our list*.
   Unsubscribe them and leave them unsubscribed until this runs its course (a
   few more days at least) or we figure out a solution and resolve it properly.
   - maintain the list of removed but valid Yahoo members and re-subscribe
   them once we resolve this issue.
   - do not allow any new yahoo.com members to join the list until we
   resolve this issue.

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