On Mon, Oct 21, 2002 at 02:41:40PM +1300, Don Stokes wrote:
- the customers have to know what they're doing;
Yes. But at some point someone has to have some clue. The real issue seems to be a large number of people with no clues who think and pretend otherwise. Fortunately, the inane desire to use sExchange is a good giveaway here.
- they have to open port 25 to at least the mail server (which inevitably means it gets opened to everyone);
No it doesn't mean this... you could open it to just certain addresses. Anyhow, so what if it does get opened to everyone?
- there is wasted dialup time waiting for the connection to get going and establishing that it has stopped.
30s or so; big deal... maybe even 2 minutes. That's typically less time than it takes to order and receive a double-cheese burger with fries.
The biggest problem with POP is getting everyone to agree what headers carry the envelope addresses, so they can be taken out when an MTA receives the message. Otherwise, it's an ugly hack that works.
POP does *NOT* work properly. There is no defined way to make it work properly and efficiently. Consider something like a 20M email to 10 people all in the same domain. This sort of thing is not uncommon. Various products have various hacks like parsing "To:" and "Cc:" headers, none of which work even remotely well.
SMTP is built around a model whereby the client can transmit on demand, and the server is always ready, and that is simply not the situation you have when you need to receive mail to dialup or mobile mail server.
Where does it say for SMTP that the "server is always ready"? It would seem a lot of SMTP smarts and indeed MTA code is to deal with the fact this isn't the case always.
POP may not be the right protocol (and I did say it was yucky), but SMTP is not the right protocol either.
SMTP was designed for transporting mail; and this is what you want to do. It makes it pretty close to the right protocol.
SMTP/ATRN is sorta the right protocol, but I'd argue that adding client functionality to a server is the wrong way to do things -- you're asking the SMTP server to do something utterly un-SMTP-server-like.
Usually, SMTP/ATRN is difficult to implement for other reasons. Some MTA products have a separation in logic (and often process and/or privileges) between the code that sends email and that which receives it. To implement ATRN, they need to violate this.
Basically, there is no right way to go about this. There is no well implemented recipient-initiated mail transport protocol.
Except, speaking from experience, not just some technically motivated idealistic view of the world, SMTP with an external trigger, in practice works extremely well.
The stupid thing about this is that uucp mail systems had solutions to these problems in production mumbleteen years ago. It's not as if the dialup model went away.
Few people put effort into making UUCP accessible to the masses (mostly work on easy of use), so it's more or less died off. --cw - To unsubscribe from nznog, send email to majordomo(a)list.waikato.ac.nz where the body of your message reads: unsubscribe nznog