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smullen0222Flag for United States of America

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Why are we being greylisted?

We run Exchange Server 2003 with Xwall Version 3.31.  Lately, many senders who have been sending to us for years are being greylisted.  I know that there can be many reasons for someone being greylisted, like being added to a greylist, heuristic checking, subject or text blocking, but on many of them,
there is no apparent reason and the messages are not dumped into the message copy folder.

I see things like:  451 4.7.1 message delayed, see ; please try again later

and 454 4.5.0 no valid recipients given.

This is becoming a real source of irritation for both the senders and would-be recipients who are all unaware that the emails are not getting thru.

I can go into Xwall Admin when it becomes known that the emails are not getting thru and tell it in the greylisting, heuristing & blocking to let these senders thru, but first you have to know who they are!

Can anyone help?
Avatar of Sembee
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Something isn't working correctly or isn't handling the greylisting messages. You shouldn't see greylisting messages. The whole theory around greylisting is that the server generates an 4.x. message which is a temporary failure. The sender shouldn't see the message, it would sit in the queue and then be delivered shortly afterwards. The idea is that a legitimate server would send again, a spammer will not.

In my experience greylisting is very effective - I have seen a high drop in spam since i have been using greylisting.

Avatar of smullen0222


Hi Simon,
     The messages that I described are in the Xwall logs.  The sender is not seeing them.  I only
see them by searching through the logs, trying to find a reason why the emails are not getting thru.
     How would we know if something was not handling the greylisting correctly?

     As it turned out, in this particular instance, the sender was sending 14mb files and the size
limit the we can receive is 10mb, but it took me a while to figure that out since nothing in the logs
stated that the email was blocked because it was too large.

     Thanks for the info that a legimate server would send again.

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I am objecting to the question being deleted as I feel I answered the question.

This question can be deleted.

For one thing, my subject was changed to "Why are we being greylisted", when it was not
us that were being greylisted, it was people trying to send to us that were being greylisted.

The solution turned to out to be a setting on the Exchange Server Recipient Policy that had
been changed.

Thanks anyway
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Force accepted.
EE Moderator