[Mimedefang] Deadline for SPF records *long w/morbid horoscope*

[Cor Bosman]

> > This is not true. Im not sure how many 'most' ISPs you are talking
> > about, but I know quite a few ISPs that accept all email for a
> > domain and forward to a customer.  This is most prevalent in
> > dialup/isdn situations where you basically 'store and forward' all
> > email for customers that are mostly offline.  When they come online
> > that triggers a queuerun towards the customer.
> 
> In many cases, this is handled not by server-to-server, but by a client 
> contacting the ISP server and retrieving the e-mail and then sorting it 
> out in whatever way.

In many other cases this is handled by MTA<>MTA traffic. 

> In any case, this is in reality no different from a client calling up 
> and getting the mail from a server.  Because the ISP is the only MX, it 
> should know about all the deliverable addresses, simply to avoid 
> dictionary e-mailings to these "offline" domains.

In theory this sounds fine, in practise this is irrealistic.
Im assuming you dont run an ISP? It would mean you would have to create
automated emailalias syncing with every customer with this type of setup, no
matter what their software is. 

> I think I confuse ISP with "quality ISP".

There is no need to be abusive to try and make your point. It makes your
point seem less valid.

> > And again, you are wrong :)
> 
> Not for "real" domains.  If the ISP is the *only* MX and you retrieve 
> your e-mail as if you are a client (not an MTA), then it is the 
> responsibility of the MX machine to know what is and is not 
> deliverable.

And that's where the heart of this confusion is. We do indeed have tens
of thousands of customers that pick up their email with client software.
POP, IMAP, even webmail. But we have quite a few customers where this
is done with MTA traffic. Customer comes online and the authentication
itself triggers a push of the queue. I know several ISPs in our area alone
that do this. 

And what do you think the command ETRN is for? One could give these hosts
a lower MX, but on the other hand, if they're almost never online you'd have
to wonder if thats a good thing. 

Dont forget, the internet is older than the spam problem. Im not saying these
kinds of setups cant be changed, im saying they're not trivial to change.
This discussion started with implementing SPF, and for an ISP implementing
SPF has a lot of problems. Not unsolvable, but it wont be pretty. 

Cor