RE: SMTP Timeout settings...

  • From: "John Tolmachoff \(Lists\)" <johnlist@xxxxxxxxxxxxxxxxxxx>
  • To: "'[ExchangeList]'" <exchangelist@xxxxxxxxxxxxx>
  • Date: Fri, 9 Sep 2005 08:49:56 -0700

I am not sure about this, I would have to look it up, but I believe e-mail
message delivery is supposed to be tried for 48 hours before being returned
if there 4.x.x. errors reported.


John T

eServices For You


-----Original Message-----
From: Chris Wall [mailto:Chris.Wall@xxxxxxxxxxxxxxxxxxx] 
Sent: Friday, September 09, 2005 6:47 AM
To: [ExchangeList]
Subject: [exchangelist] SMTP Timeout settings...

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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