Courier and DCC

Vernon Schryver
Wed Apr 10 01:15:21 UTC 2002

> From: Vincent Schonau <>

> ...
> - courierfilter is an API that allows you to write your own (globla)
>   filters to process e-mail during the SMTP conversation. An interface
>   to perl filters is also provided, so it should be fairly easy to
>   create a filter that will pipe the mail through dccproc before
>   accepting it, and even possibly reject it based on the dccproc output.
>   courierfilter can't modify the message, however, so DCC headers can't
>   be added here.

Is there some way the MTA could call a persistent process?
All of this fork()ing and exec()ing makes me wonder about performacne.

> ...
>   provides pre-defined filters in a special place. Calling dccproc
>   through maildropfilters 'xfilter' looks like the best option. The
>   filters are executed as the recipient who owns the filter, so
>   $HOME/.whiteclnt will be accessible. The filters are executed during
>   the smtp-conversation, and can only accept or reject a message, not
>   change it (so no headers).

The lack of headers would hurt dccproc whitelisting.  What else 
can be used for whitelisting (besides the envelope Mail_from value)?
(I've found the envelope HELO value handy for blacklisting).

> ...
>   options above and have users put dccproc -Q in their mailfilter to add
>   headers for (further) filtering, or you could provide _no_ DCC
>   services at the server-wide level and simply have users call dccproc
>   from their mailfilters (using xfilter).

> ...
> SMTP-level options, perhaps a cripled query-only version of dccproc
> available to users would be useful.

What would be the difference between that crippled, query-only
version and `dccproc -Q`?    The point of `dccproc -Q` is to
query the DCC server without reporting.

> There was some public discussion (in nanae, I think) between the authors
> of Courier and DCC respectively that would indicate that there's not
> much chance of extensive support for DCC in Courie. I think it'd be very
> cool to have a dcc client that implements the courierfilter interface,
> though, so if anyone is going to write one, I'll volunteer as a tester

I don't recall anything about Courier in NANAE, but perhaps I'm confused
or forgetful.

Vernon Schryver

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