On Tue, 26 Jun 2001, Chris Crowther wrote:
> Well that's me, but my dialup does have a static IP, and is the
> listed primary MX for all my domains (I have other mail servers to hold
> the mail if I'm not on).
That is anti-social, IMHO, assuming you are dialled up for only a
fraction of the day.
Every server that wants to send you mail is going to try to contact your
primary MX, find you are not there (usually), hang around till it times
out (usually 5 minutes) and then go to the secondary. So you are causing
it to use resources (process, space, etc) for that 5 minutes. If the
server is intelligent, it will of course remember that your primary was
down, and not try it again for some time, which will help.[1] However,
some mailers do retries *per message* (not per host, as Exim does) so
they are going to have this waste for every message. I know it's not
much, but it all adds up. It can also cause other problems.[2]
In my view, no dial-up host should ever be an MX primary.
> I don't see why I should use my ISP's mail server when I have
> fully functioning one of my own.
I don't consider it to be "fully functioning" unless it is intended to
be running 24x7. Sorry to sound harsh, but it's just my opinion, of
course.
---------------
[1] If the sender is Exim and it "always" finds your host down for long
enough, it will (with default configuration) go onto a very long-term
retry schedule (8 hours).
[2] Some years ago I came across a case where a host behind a firewall
was in this state (primary MX -> inaccessable host). A different host
on an ISDN line was trying to mail to it. That host was configured so
that if activity on the line was zero for long enough, it dropped the
connection. Unfortunately, the line timed out before the mailer timed
out....
--
Philip Hazel University of Cambridge Computing Service,
ph10@??? Cambridge, England. Phone: +44 1223 334714.
