On Sat, 14 Nov 1998, Philip Guenther wrote:
era eriksson <era(_at_)iki(_dot_)fi> writes:
...
3. You can pretend to get along by simply ignoring the above facts,
and create a bigger problem than you had to start with by trying
to kludge around the problems that inevitably crop up by and by,
as you encounter them. This has proven to be an incredibly popular
option. Granted, a lot of the time a lot of the information you
need is coincidentally in the headers, and some fairly big sites
who ought to know better are relying on this for mail delivery.
For example, fetchmail, I believe, rather successfully uses #3.
Fetchmail would prefer to look for the recipient address(es) in a
specified header (i.e., the last part of #2), but since many places
can't or won't do that, it's probably stuck doing #3 most of the time.
I believe qmail can be configured to insert envelope information into a
special set of headers which are then deleted again by the qmail delivery
agent. I'm not that great a fan of qmail, but if you can convince your
ISP to use it for delivery to your POP drops, you can then feed the
messages to a local copy of the qmail delivery agent after popping them
down, and everything works. This is effectively using POP as a remote
mqueue area, by keeping the delivery data in headers instead of in a
separate file.
Conceivably a "better" protocol for this would use some kind of MIME
encapsulation, but DJB is a fanatic for minimizing the amount of data on
the wire, so I'm sure he made the choice to avoid encapsulation overhead.