[KLUG Members] sendmail relaying question

[bill]

Thanks, Justin.

Thoughts below

Buist Justin wrote:

> It's locating the destination SMTP server for that given user and delivering it there for you.

So my sendmail box is doing the negotiation with the recipient's server?

> The only thing your ISP could do to stop this is block all outgoing connections to port 25 -- which Mindspring/earthlink did to me when I was a DSL customer of theirs.  Pulled my hair out for 2 hours trying to figure out why the SMTP server I had just setup wouldn't work outside the office ('twas testing it from an ssh connection back home).  I wasn't happen when I found that out.
>
> You -could- configure sendmail to use your ISP's SMTP server as a "smart-host" if you want, in which case you would be relaying all of your mail  through the ISP who would then deliver it to you.

If I'm understanding correctly, you mean "deliver it -for- you" here.

> I don't see much point in this though, unless you start getting bounce-backs from people who won't accept delivery from you because your server looks like a SPAM server.  I've seen a flurry of network admins do this over the past few years -- blocking an SMTP server because there's no reverse-ip lookup, or the lookup doesn't match, etc.

So, although the ISP isn't technically an open relay, because I'm not really using their SMTP server, I still might get things blocked down the road because my sendmail box isn't an "official" smtp server?

thanks,

bill

>
> > -----Original Message-----
> > From: bill [mailto:bill@billtron.com]
> > Sent: Friday, November 22, 2002 10:13 AM
> > To: members@kalamazoolinux.org
> > Subject: [KLUG Members] sendmail relaying question
> >
> >
> > Trying to master sendmail, I've set it up to handle outgoing
> > mail for a home
> > network.  Seems to work fine.  Now I'm wondering how.
> >
> > It makes me think about relaying.  Not my computer, but the
> > ISP.  It obviously
> > isn't blocking ports, but is the ISP an open relay?
> >
> > My sendmail box is set to prevent relaying (sending mail)
> > from anybody but
> > designated machines on my network.  But the sendmail box
> > knows nothing about my
> > ISP.  Should I somehow configure sendmail to say it is part
> > of the ISP's
> > network?
> >
> > I'm using a dynamic ip address with broadband (dsl), so if
> > the e-mail is going
> > out through my linux mail server, the ISP is just accepting
> > it and sending it
> > out.  Does that mean they are technically an open relay?  Or
> > is sendmail
> > locating the destination pop3 server and doing negotiations directly?
> >
> > kind regards,
> >
> > bill hollett
> >
> >
> >
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> > Members@kalamazoolinux.org
> > 
> >
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