[KLUG Members] sendmail relaying question

[Buist Justin]

> 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?

You got it.


> > 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.

Yep... directional dyslexia.
 
> 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?

Not exactly.  An "open relay" is an SMTP service that accepts delivery for people it shouldn't.  Your SMTP server should only attempt to deliver mail that is either:
a)  Local -- if a piece of mail I'm handed is to be delivered by me I'd better not drop it.
b)  From somebody on your network (customer, co-worker, etc).

As somebody else said, don't confuse TCP/IP routing with SMTP relaying.

I wouldn't say "official", but perhaps "not configured exactly right".  Way back in the day when I started messing with this stuff I actually had an SMTP server that would send out 'HELO localhost' .... basically because I didn't know any better.  That'd get blocked by some servers.

Justin Buist