Re: Exim as a LAN mail server [possibly-OT]
In article <[🔎] 20010714153744.B2234@animus.fel.iae.nl>, Carel Fellinger
wrote:
> On Sat, Jul 14, 2001 at 06:35:53PM +1000, mdevin@ozemail.com.au
wrote:
> > However, I think that exim by default will continue to send the
message
> > for 4 days before giving up. So long as you connect several times
> > within these 4 days and flush exims que each time then there is a
very
> > good chance the mail will get sent. I have a script in the
>
> Only if the destination machine is on the net too in those few
moments
> that you are. Imagion that you are to send mail to my mail server
> directly, then it's quit likely that, though I'm on the net for
> atleast 12 hours a day, you still miss me because my daytime differs
> from yours, living on the other side of the world and all that. Were
> you to use your ISP's mail server, changes would go up remarkably,
> just because that machine is on the net during your nighttime / my
> daytime. Best would be if we both used our ISP's servers, then the
> mail would get delivered instantaniously, so less resources used.
I think this is misleading.
SMTP mailers, when sending mail "direct", first look up the
destination's MX record in the DNS. The MX record will normally (I mean
"always, unless the destination's configuration is screwed") point to
an SMTP server which is permanently (I mean "barring breakdowns")
connected to the net.
If the destination machine does not have a permanent connection, the MX
address usually points to the SMTP server of an ISP. That server will
then either store the mail in a POP/IMAP/whatever server, or forward
the mail via SMTP/UUCP/whatever to the ultimate destination when it
next connects.
Naturally, this being the Internet, there will probably be more than 1
MX record, the others pointing to backup servers to use if the main
server is down. And, of course, it isn't always quite that simple,
because there may be multiple hops between the MX server and the
ultimate destination.
--
Nikki Locke, Trumphurst Ltd. PC & Unix consultancy & programming
nikki@trumphurst.com http://www.trumphurst.com/
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