[elspy] usual questions about suitability
gward at python.net
Sun Aug 22 00:56:25 CEST 2004
On 18 August 2004, Eric S. Johansson said:
> the ability to rewrite recipients both in terms of number of and modify
> their e-mail addresses. This also includes the ability to declare a
> message as having vanished from the MTA's awareness (in other words,
> it's been consumed by the anti-spam filter).
As Andrew pointed out, you can do this in local_scan(), including an
elspy local_scan(). (I think the only functionality I didn't implement
was the ability to change headers. Or maybe to remove them. Don't
remember, it's been a while, and my attitude has been, "I'll implement
that when I need it". So far I haven't needed it.)
Removing all recipients instructs Exim to blackhole the message, which I
think is what you want. (Although, like Andrew, I would counsel against
blackholing messages in all but dire circumstances. Oh, wait,
delivering email these days is a dire circumstance. Sigh.)
> the ability to limit the number of filter instances running at any one
> time. There are many things that camram does that works relatively well
> in a multitasking environment but there are a few things that just
> consume every ounce of CPU you have and then some for a few moments.
> Those operations really want to be single threaded.
You can't do that with elspy (or with any Exim local_scan()), because
you have no way of knowing how many exim processes are running at a
time. I agree with Andrew here: you probably need a separate daemon
process, not something running in the MTA's process-space. SpamAssassin
does the same thing (spamd/spamc), probably for much the same reasons.
> the ability to distinguish which interface the traffic comes from or the
> ability to bind filter to interface.
Err, not sure, but probably. Check Exim's fine manual -- the chapter on
local_scan() in particular. Note that elspy doesn't necessarily expose
all the global variables in Exim 4.4, since I wrote it for Exim 4.1 or
4.2 and haven't updated the list of variables since then. (Again, I'll
do it when I need it, but haven't needed it yet. Patches welcome.)
> I have a concern about the life/support/viability of the filter
> interface because it's really painful putting in a lot of work to use a
> filter interface only to have the filter interface become unsupported
> for goodness knows what reason. I've acquired this little bit of scar
> tissue one time too many. ;-)
It's hard to comment on the future of elspy. It doesn't seem to have
taken the world by storm, judging by the traffic on this list. Maybe I
just wrote such amazingly good docs that nobody needs to ask questions.
> since there are two python interfaces to exim, it would be nice to know
> if either one of them was "officially" supported by the exim community.
Don't think so. I still can't understand why everyone doesn't use Exim
for an MTA and want to filter their mail with Python, but that's just
Greg Ward <gward at python.net> http://www.gerg.ca/
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