Re: newby question for libesmtp & sendmail

[Brian Stafford <brian stafford uklinux net>]

On 2001.06.16 09:01:29 +0100 brokkolo wrote:
> i work on a home machine (dialup) with sendmail,
> if i don't compile libesmtp support i can send mail throwgh sendmail
> without having it running (not sure of the tec term but sendmail fires up
> when i send mail...).

In this case, Balsa submits mail by fork/exec of send mail and sending
the message to it via a pipe.

> compiling libesmtp support (an wanting to use my sendmail and not relay
> on isp mta) i need to have sendmail running as deamon... so he is
> listening on port 25... (localhost:25) 

correct.

> is it possible to use libesmtp for isp mta, and then change to local
> sendmail but not having it to be listening and running on port 25? can

This type of fallback behaviour is not possible and is not likely to
be implemented either.  LibESMTP does have the capability to use
multiple servers for load balancing and redundancy if one of them is
down but this is a feature of the way it uses DNS.

> libesmtp pass the mail to sendmail the way balsa does when not compiled
> with esmtp support?

There would be no point in doing this, libESMTP is an SMTP client.

However, there is a way a similar effect can be obtained if you have
root access to your system.  Edit /etc/services and add the following
line if it is not already present.

submission       587/tcp                          # Mail Submission

Then edit /etc/inetd.conf and add the following line.

submission stream tcp nowait root /usr/sbin/tcpd /sbin/sendmail -U -bs

or if you dont use tcpd

submission stream tcp nowait root /sbin/sendmail sendmail -U -bs

kill -HUP the process id for inetd and it will run sendmail for you
each time you connect to port 587 - which happens to be the default port
used by libESMTP.  Configure Balsa to use a remote SMTP server of
"localhost" (no :25 needed).

> (what is the main difference with having sendmail befave the first way or
> as deamon?)

I asked this question of some sendmail gurus a while ago and was told that
there is essentially no difference - when you fork/exec sendmail it omits
an anti-spam check.  Other than that, sendmail processes the messages
identically.

Regards
Brian Stafford