SMTP Timeout settings...

  • From: "Chris Wall" <Chris.Wall@xxxxxxxxxxxxxxxxxxx>
  • To: "[ExchangeList]" <exchangelist@xxxxxxxxxxxxx>
  • Date: Fri, 9 Sep 2005 09:46:48 -0400

Hello all,


   Just curious - how many of you edit the default timeout settings on
e-mail delivery?  My question is in regards to Delay Notifications and
when to stop retrying delivery of a queued message.


   I have set fairly aggressive Outbound and Inbound limits of:


Delay Notification - 30 Minutes

Expiration Timeout - 4 hours


(Of course I have edited the retry intervals appropriately so that at
least 4 delivery attempts occur before Expiring/Failing the delivery)


    In the past, before Spoofing/SPAM was so prevalent, I had larger
values.  But with the amount of illegitimate e-mails today and queued
Non-delivery replies from our systems (as a result of Dictionary
Attacks) I have decided to cut down on the time allotted to retry
delivery of messages.  Also, so many companies have multiple MX records
for their domains, I see no reason to keep the default Expiration
Timeout (Failure notification) of 24 hours.


    I have implemented LDAP lookups so messages that are addressed to
non-existent e-mail accounts are simply deleted.  This helps greatly,
but if a dictionary attack does have at least one valid e-mail address,
it is relayed into our Exchange systems for delivery.  This means
occasionally there will be a large number of automated replies to the
SPAMMER indicating the message could not be delivered because the
recipient does not exist (as I have to do in accordance to e-mail
regulations).  These settings so far have helped to keep our outbound
queues at a minimum.


     Is this too aggressive or do most of you agree with these settings?


Thanks for the input.


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