Request for assistance

[mark at buttery.org (Mark J. Dulcey)]

John Chambers wrote:
> 
> These packages should all be capable of connecting directly
> to  the  recipient's  machine  (or  MX server).  Is there a
> reason you're using the ISP's server for outgoing mail?
> 
> There's really no sensible reason to do this.  If you're on
> the  internet,  all you have to do is make a TCP connection
> to the recipient's port 25 and start talking SMTP.  You can
> do  this  with  telnet (if you know SMTP, which is an ascii
> protocol, and fairly easy to type).
> 
> If you're running Windoze, you might not have a choice. But
> on  a  unix-like  system,  all  that  bouncing email off an
> intermediate server does is increase  network  traffic  and
> delivery  time.   If  you can configure your email stuff to
> make direct delivery, you can avoid your ISP's restrictions
> and get faster delivery.

Actually, none of the usual email clients normally make delivery directly to the recipient. They're all normally set up to send email to one specific SMTP server. You can, however, set that server to be whatever you want. To send directly to the recipient, you would have to reconfigure your mail client each time you sent a piece of mail, which would be a colossal pain.

And there is a good reason why it's done that way. Client software usually sends mail SYNCHRONOUSLY; that is, the software, or at least the mail client portion of it, is tied up until the mail is sent. (Outlook Express and Eurora are exceptions; they send in the background.) Furthermore, the recipient isn't always available right away; his email server might be down, or there might be a problem in the Internet somewhere between point A and point B.

That's the reason we have SMTP servers in the first place. It's their job to do things in the background, to keep trying if they don't succeed immediately, and (typically) to log everything they do. Having a server to do that simplifies the job of the mail client; it means that you have to write all that bulletproof code only once, instead of once for each client.

If you have a full-time Internet connection with a static IP address, run your OWN server by all means. (Every Linux distribution these days comes with sendmail, postfix, or some other SMTP server software, and makes it easy to set up, at least in the simple cases.) That keeps the extra traffic off the Internet (your LAN presumably has plenty of capacity for it), and gives you the advantage of full control over your email. But, in a previous message, I pointed out the problems of running your own server if you don't have a full-time connection. That's exactly when an SMTP server at your ISP should be making life easier instead of harder.