||Configuring Your Virtual Server For Mail-On-Demand
If you wish
to implement Microsoft Exchange Mail-On-Demand
you must first Configure Your Exchange
Server for Mail-On-Demand and then follow the steps
You should carefully consider the following.
e-mail (incoming and outgoing) will be held in
the queue until it is flushed out, either by an
ETRN command or the flush command in your crontab.
This means that if your crontab is set to flush
every 4 hours, an outgoing e-mail could wait 4
hours before it is sent from your VPS.
Mail dequeuing will affect all domains
hosted on your VPS. So, only one domain should
be hosted on your VPS unless all domains
on the server are using the mail dequeuing feature
the MX records for the domain name with the 10 level pointing
to your Exchange Server and the 20 level pointing back
to your VPS.
your VPS to queue up e-mail until the ETRN command is
received by your Exchange Server.
Add the following line to the Options section of the
~/etc/sendmail.cf file on your VPS:
Odqueueonly # defer mail on the server
Comment out the following two lines in Ruleset 0:
R<@60w> >90 Remove local addresses
R<@60w>0 >90 Remove local routes/UUCP
These two lines let the server know what domains are
local to your Virtual Server. For mail dequeuing,
no domain should resolve locally.
Add the following line to your VPS Crontab
00 0-23/4 * * * /usr/local/bin/virtual sendmail -q
This will flush out your VPS mail queue every four
hours. You may need to modify this according to how
long your Exchange Server may be off line. Every time
an attempt is made to flush the queue, a hop is added
to the headers for each message queued up. This means
that if you set your crontab to flush the queue every
15 minutes then an additional hop would be added every
15 minutes. This would mean that after 6 hours in
the mail queue, a message would have 24 hops (where
the maximum is 26). Therefore, any e-mail older than
6 1/2 hours would be bounced with "too many hops".
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