If "telnet mail.yourdomain.com 25" gives a connection refused, then it's
either a firewall issue, or Sendmail is not listening on port 25 for
mail.domain.com (I've seen some unixes start a local-only Sendmail on port
25, so it only accepts connections from/to "localhost:25"  Check how
sendmail is started in your start-up scripts, or see what the actual
command-line was in /proc (or does Sendmail change this.../)

If telnet mail.domain.com 25 gives you the SMTP banner, and you get
"relaying denied" from Sendmail while trying to actually send a message,
then you need to tell Sendmail to relay mail for the domain you're trying
to be backup for.  This may be /etc/mail/relay-domains, you can see what
your distro calls it by grepping for "FR-o" in your sendmail.cf (assuming
it's configured to use a file), or "cR-o" if it doesn't use a file (i.e.,
they are specified in your sendmail.mc file).

If it's a Sendmail issue and not a firewall/IPtables issue, contact me off
list and I can provide some more help if needed (include your
sendmail.cf).

Adam Maloney
Groks Sendmail Rulesets :)
Sihope Communications

On Sat, 11 Oct 2003, gkrueger wrote:

> Hi All:
>
> I'd love some advice as I'm running out of ideas.  I've been attempting
> to set up a second mail server as a backup and, for the life of me, I
> cannot understand why it won't relay messages through port 25 (smtp).
>  I've checked iptables -- I even flushed all iptable rules just to test
> -- then I added explicit "ACCEPT" rules to tcp and udp port 25 in iptables.
>
> For some reason, this machine (running redhat 8 with sendmail) will
> send/relay, and receive both internal and external email if I use pine
> or mail.  However, if I use a browser client like mozilla or outlook,
> relaying is automatically denied -- yet the maillog posts no message as
> to why it's denied.  I'm pretty sure I set outgoing server correctly in
> the browser: "mail.domain.com" and I added "domain.com" to my access.db
> along with the network IP address (then ran makemap and restarted sendmail).
>
> Furthermore, I activated telnet and tried to "telnet  mail.domain.com
>  25" and the connection was refused (yet standard telnet to port 23 was
> accepted).  I"m thinking it might be something in sendmail.cf, but I'm
> not sure.
>
> Can anyone think of some obvious things which might be blocking relay?
>  I'm fresh out.
>
> Thanks!
>
> Garrett
>
>
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