On Mon, Dec 23, 2002 at 07:45:03AM -0500, Mike Burger wrote:

> You're mistaken.  Exchange doesn't inform users of anything.  The Outlook 
> client informs the user of new mail...after it's polled the Exchange 
> server to see what's there.

Partially. Exchange server has the ability to inform a MAPI client that
a new message has arrived. So Outlook can inform the user. thus, the
original poster's observation is correct from a user's point of view.

As to the original question, there are several facts to consider if you
try to do something like this:

1. Exchange is not only a MTA, but also a POP and IMAP server (as well
as a MAPI server).
2. Sendmail is only an MTA.
3. Your mail clients interact with a linux based mail server through POP
or IMAP to get received messages. SMTP is used only to send messages.

To the best of my knowledgem there is no POP or IMAP server which can
notify clients of new message arrivals. So, the closest you can get to
the Exchange behaveiour, is to configure clients to poll the server
often. I do this at 5 minute intervals, since I have no use for finer
granularity, but there is no reason preventing me from setting this
interval at 1 minute. If I wanted to go further down, I would have to
change my message retrieval method (I run fetchmail from crontab), due
to cron's timer granularity, but the server shouldn't refuse my
connections.

If you try this, note that a large number of clients could bring an
xinetd based POP or IMAP server down if set to poll too often. But this
is a feature of xinetd, which closes services that get polled too many
times in a small span of time, so as to prevent a full systemwide crash.
This threshold is configurable. I don't recall the parameter off the top
of my head, but I'm positive it's somewhere on ther man pages (either
xinetd or xinetd.conf).

Cheers,
-- 
Javier Gostling                        Av. Kennedy 5757, of. 1502
Ingeniero de Sistemas                  Las Condes, Santiago, Chile
Virtualia S.A.                         Fono: +56 (2) 202-6264 x 130
[EMAIL PROTECTED]                 Fax:  +56 (2) 342-8763

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