I started noticing the following on a mail server I administer.
relay=mx2.mail.yahoo.com. [64.156.215.6], dsn=4.0.0, stat=Deferred:
421 VS14-PR Mailbox bounce arrival rate exceeds system limit (#4.2.2)
In this particular case a user's email is forwarded to her Yahoo email
account. Nearly all of it is spam and is being tagged as such by
Spamassassin, but she wants it forwarded to her Yahoo account. The mail is
just queuing and building up.
I analyzed attempts to deliver to her Yahoo account for a single hour from
this afternoon.
491 attempts - dsn=5.0.0, stat=Service unavailable
158 attempts - dsn=4.0.0, stat=Deferred: 421 VS14-PR Mailbox bounce arrival
rate exceeds system li
mit (#4.2.2)
209 attempts - dsn=4.0.0, stat=Deferred: Connection reset by
mx4.mail.yahoo.com
I've successfully sent mail from the server to other yahoo.com accounts. It
appears that Yahoo has implemented a mechanism which limits the rate at
which email from a host can be delivered to a specific yahoo.com user.
Have any of you seen this on your mail servers? And do any of you know what
the max arrival rate is or how I can find out? I'm also interested if this
has affected your mailing lists. I haven't run into it on any of the lists
I manage (I checked logs a few hours ago), but since Yahoo users make up b/w
5% and 15% of the subscriptions on most of my lists I'd like to be prepared.
--
Steve Werby
President, Befriend Internet Services LLC
http://www.befriend.com/
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