Date: Tue, 28 Jul 1998 11:25:46 -0700 (PDT) From: David Wolfskill <dhw@whistle.com> To: questions@FreeBSD.ORG, sderdau@bit-net.com Subject: Re: email question. Message-ID: <199807281825.LAA00814@pau-amma.whistle.com> In-Reply-To: <Pine.OSF.3.95.980728120246.15623A-100000@mail.bit-net.com>
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>Date: Tue, 28 Jul 1998 12:28:30 -0400 (EDT)
>From: Stephen Derdau <sderdau@bit-net.com>
>Why would email sent by a user sderdau%mcl
> be delivered and showing from sderdau@mcl instead of
>sderdau%mcl@qualified.domain.com.
Because of the (in)famous "percent hack".
>Pointers in the write direction appreciated.
>I know this is probably a sendmail question . Just hoping
>someone with great expertise wouldn't mind answering it.
OK; a partial list:
pau-amma[36]% grep -B 2 -A 1 -n '%' /etc/sendmail.cf
91-
92-# operators that cannot be in local usernames (i.e., network indicators)
93:CO @ % !
94-
--
367-
368-# delimiter (operator) characters (old $o macro)
369:O OperatorChars=.:%@!^/[]+
370-
--
483-R$+ ! $+ $@ $>96 $2 < @ $1 .UUCP > uucp subdomains
484-
485:# if we have % signs, take the rightmost one
486:R$* % $* $1 @ $2 First make them all @s.
487:R$* @ $* @ $* $1 % $2 @ $3 Undo all but the last.
488-R$* @ $* $@ $>96 $1 < @ $2 > Insert < > and finish
Or, to put it another way, the '%' is effectively replaced by '@'.
It was a technique for allowing email with "foreign" addressing conventions
such as old "bang-path" UUCP, or BITNET, or various other approaches to
be gatewayed to & from the Internet.
Ideally, it would have become an endangered species by now.... :-{
david
--
David Wolfskill UNIX System Administrator
dhw@whistle.com voice: (650) 577-7158 pager: (650) 371-4621
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