[Mailman-Users] Ongoing delivery issues - First Yahoo, now AOL

[Matt Morgan]

On Fri, Mar 7, 2008 at 2:58 PM, Mark Sapiro <mark at msapiro.net> wrote:
> Rick Harris wrote:
>  >
>  >I posted a couple of weeks ago regarding mail not being delivered to Yahoo
>  >addresses.  I've all but written that off as an Internet black hole.
>  >Messages from my list almost never make it to Yahoo recipients.  If I post
>  >to the list, and cc a Yahoo address, then that works fine.  Background noise
>  >only, none of this matters today.
>
>
>  Since your original post on this issue, I have looked at my maillog and
>  I see lots of these
>
>  host e.mx.mail.yahoo.com[216.39.53.1] refused to talk to me: 421 4.7.0
>  [TS01] Messages from 72.52.113.16 temporarily deferred due to user
>  complaints - 4.16.55.1; see http://postmaster.yahoo.com/421-ts01.html
>
>  type messages (3500 in the last month, but only 46 in the last 5 days).
>  I also get lots of
>
>  host g.mx.mail.yahoo.com[206.190.53.191] said: 451 Message temporarily
>  deferred - [250] (in reply to end of DATA command)
>
>  and
>
>  host c.mx.mail.yahoo.com[216.39.53.3] said: 421 Message temporarily
>  deferred - 4.16.51. Please refer to
>  http://help.yahoo.com/help/us/mail/defer/defer-06.html (in reply to
>  end of DATA command)
>
>  and
>
>  host c.mx.mail.yahoo.com[68.142.237.182] refused to talk to me: 421
>  Message temporarily deferred - 4.16.55.1. Please refer to
>  http://help.yahoo.com/help/us/mail/defer/defer-06.html

This is greylisting:

http://greylisting.org

in which the receiving MTA responds with a temporary failure to
suspicious or unknown senders. It kills a lot of spam, because most
spam is sent by non-compliant MTAs that don't bother retrying.

>  The important thing is that in my case at least, every one of these is
>  successfully retried, either immediately via a different MX or after 1
>  or a few delayed retries. All of these messages were eventually
>  accepted by Yahoo and I have gotten zero complaints of missing mail
>  from Yahoo list members.
>
>  Perhaps there is some issue with your outbound MTA not retrying these
>  421 and 451 status returns.

Ditto. Rick, are you in charge of your MTA? One way or another, you
should figure out how your MTA handles temporary failures and retries.

--Matt