Trevor,

The problem may be at your end.  (Have you changed anything there
recently?)  My reply to your address bounced when sent from my sendmail
server, which hasn't changed in a long time.  Here's what I got in the
bounce message...

    ----- The following addresses had permanent fatal errors -----
<trevor@tecnopolis.ca>
     (reason: 550 <trevor@tecnopolis.ca>... 451 4.7.1 Greylisting in
action, please come back later)

    ----- Transcript of session follows -----
... while talking to tecnopolis.ca.:
 >>> DATA
<<< 550 <trevor@tecnopolis.ca>... 451 4.7.1 Greylisting in action,
please come back later
550 5.1.1 <trevor@tecnopolis.ca>... User unknown
<<< 503 5.0.0 Need RCPT (recipient)

--v7HEwiKb114371.1502981924/copper.cs.umanitoba.ca
Content-Type: message/delivery-status

Reporting-MTA: dns; copper.cs.umanitoba.ca
Received-From-MTA: DNS; lockwood3.cs.umanitoba.ca
Arrival-Date: Thu, 17 Aug 2017 09:58:37 -0500

Final-Recipient: RFC822; trevor@tecnopolis.ca
Action: failed
Status: 5.1.1
Remote-MTA: DNS; tecnopolis.ca
Diagnostic-Code: SMTP; 550 <trevor@tecnopolis.ca>... 451 4.7.1
Greylisting in action, please come back later
Last-Attempt-Date: Thu, 17 Aug 2017 09:58:44 -0500

On 17/08/2017 3:22 AM, Trevor Cordes wrote:
> I just started getting some weirdness with some email sent to my mail
> servers.  Greylisting "come back later" (451) messages are being
> interpreted (it appears) by remote MTAs as a 5xx level error, meaning they
> immediately abort send attempts and bounce the email!  I have never seen
> this before.
>
> I've seen it from two separate remote MTAs so far, but from reports I'm
> getting in, it's happening on more.
>
> Here's what I get from umce3cip03.ad.umanitoba.ca:
>
> Remote Server returned '554 5.0.0 <[50.71.247.87] #5.0.0 smtp; 5.1.0 -
> Unknown address error 550-'<foobar@tecnopolis.ca>... 451 4.7.1 Greylisting
> in action, please come back later' (delivery attempts: 0)>'
>
> On my server sendmail log I see:
>
> Aug 16 08:43:15 pog sendmail[14379]: v7GDhFav014379: Milter:
> to=<foobar@tecnopolis.ca>, reject=451 4.7.1 Greylisting in action, please
> come back later
>
> So umce3cip03.ad.umanitoba.ca appears to be taking my 451 and turning it
> into a 500/554/510 permanent error.
>
> I also see this from yahoomail, but that's a different situation because
> yahoo is always considered "broken mta" in milter-greylist and we must
> whitelist all of their servers... but, the usual/previous symptom was
> yahoo would keep retrying as normal, just with a different IP each time,
> thus never passing greylisting.  And now yahoo is doing the same thing as
> umce3cip03.ad.umanitoba.ca above (when I haven't yet whitelisted the
> particular IP that day, grrr):
>
> Sorry, we were unable to deliver your message to the following address.
> <foo@tecnopolis.ca>:
> 550: <foo@tecnopolis.ca>... 451 4.7.1 Greylisting in action, please
> come back later
...

--
Manitoba UNIX User Group        E-mail: <gedetil@muug.ca>
c/o Gilbert E. Detillieux       Web:    http://muug.ca/
University of Manitoba          Phone:  (204)474-8161
Winnipeg MB CANADA  R3T 2N2     Fax:    (204)474-7609
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