From: Holger.VanKoll@SWISSCOM.COM
Date: Wed Aug 21 2002 - 06:31:16 EDT
> When I ran sendmail -bp it reported "There is 1 request in
> the mail queue"
> which is what I would have expected however shortly after
> that the email
> was delivered.
Yes, because...
> Can someone explain what the sendmail daemon process is for
> (just receiving
> mail?)
... this is correct. The sendmail daemon accepts mail with SMTP on port 25.
To send mail, the (called) sendmail binary contacts the corresponding sendmail-daemon, for local mail the sendmail daemon on the local host, for remote mail the daemon on the remote host.
So if you stop the daemon, local mail wont be delivered. (at least not from remote hosts).
> and if I leave the sendmail daemon down can I always expect
> immediate delivery of emails send from the system?
Yes, but it depends how mail is send. Most programs call the local sendmail-binary and leave everything up to it.
A program could be written in a way that it will work if sendmail is not installed, but something else (qmail etc.). This programm wont rely on having a sendmail binary to do the work and try to deliver it by SMTP itself.
It would still work for remote mail if it cares about the MX (f.e. does an nslookup -q=mx hostname).
It could however be written in a way to contact the local MTA for delivering. Then, it wont work; not for local and not for remote mail.
A strings progname|grep sendmail should be enough to check this; or call any programm and do an ls -lu /usr/sbin/sendmail.
The normal case is, however, to call the sendmail binary like mail does.
Regards,
Holger
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