Re: Why does sendmail depend on procmail?
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On Sun, 12 Oct 1997, Christian Schwarz wrote:
> On 7 Oct 1997, Manoj Srivastava wrote:
> > >>"Fabrizio" == Fabrizio Polacco <firstname.lastname@example.org> writes:
> > Fabrizio> Someone else suggested a /usr/sbin/mda wrapper installed by
> > Fabrizio> each mda's package using the usual alternative method. You
> > Fabrizio> could agree on its interface in sendmail.cf; something like
> > Fabrizio> that:
> > Fabrizio> sendmail.cf:
> > >> A=/usr/sbin/mda $g $h $u
> > Fabrizio> and deliver's mda :
> > >> deliver -r $1 $3
> > Fabrizio> while procmail's mda:
> > >> procmail -Y -a $2 -d $3
> It would be nice if someone could provide me with some text I can include
> in the policy manual. (I don't know enough about MDAs so I don't think I'd
> be the right author for this.) After I got the text, I'll include it in my
> POLICY WEEKLY postings for approval.
Okay, please let me head this off before it gets any further. Johnie
Ingram (sendmail's maintainer) and I (deliver's maintainer) have discussed
the above idea in IRC, and basically concluded that it was sub-optimal.
There are a few problems with creating a generic MDA script:
1. deliver and procmail have slightly different capabilities. Sendmail
currently detects which one is installed (it give the option of which
to use if both are installed) and configures itself to optimally use
the delivery agent present.
2. Using a shell script means that a shell has to be fired off for every
local mail delivery. This is an extra program load that over doubles
the overhead of mail delivery. /bin/bash is about 6 times larger than
procmail and almost 8 times the size of deliver. This is overhead
that is avoided by allowing sendmail to call one of them itself.
3. Sendmail (which is the only MTA not using a builtin MDA by default) is
labeled as extra in its priority field. An admin who actually
installs it instead of smail should probably understand that they
shouldn't yank its MDA out from under it. I've added a check in the
prerm of deliver for sendmail using it, and deliver will refuse to
uninstall itself (prompting the admin to reconfigure sendmail) if it
detects this to be the case. If procmail is modified to do the same
check, it shouldn't be possible to remove sendmail's current MTA.
Sendmail can be set back to requiring mail-transport-agent instead of
procmail (which is what started this whole debate) and everything
| Do not, I beg you,
Scott K. Ellis | look for anything behind phenomena.
email@example.com | They are themselves their own lesson.
| -- Goethe
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