Hello,

Once in a while I havce to send out a message to thousands of users from a
variable set.  So, I make a custom database query to extract the recipients
list. Then I establish a SMTP connection to a qmail server.

My problem is that along the time the number of recipients has been growing
to many thousands but the time that queueing takes does not grow linearly
with the number of recipients but rather grows exponentially.

I am taking advantage of the PIPELINING SMTP extension to reduce the overhead
of waiting for the response from the STMP server.  I take care of not pipe
more than 100 recipients at a time before waiting for the server response
to all to not exceed the TCP window size to avoid SMTP dialogue deadlock.

Once I decide to make my connection code to output the dialogue between the
SMTP client and the server and I noticed that periodically the dialogue hangs
for a little while and then it proceeds. Response hang periods do not happen
right after queing the current batch of 100 piped recipients.

Does anybody know how to explain this?  Is there a cure?  Would spliting
the queueing in many different messages help?  If so, how many recipients
are recommended per batch?



Regards,
Manuel Lemos

Web Programming Components using PHP Classes.
Look at: http://phpclasses.UpperDesign.com/?[EMAIL PROTECTED]
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