SMTP question - ReadList.com

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SMTP question
\ Tom Allison (12 Jun 2007)
. \ Victor Duchovni (12 Jun 2007)
. . \ Tom Allison (13 Jun 2007)
. . . \ Victor Duchovni (13 Jun 2007)
. . . . \ Tom Allison (13 Jun 2007)
. . . \ (Wietse Venema) (13 Jun 2007)

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Subject:	SMTP question
Group:	Postfix-users
From:	Tom Allison
Date:	12 Jun 2007

I'm trying to write a proxy in perl and ran into a problem that I can't seem to
get around and I'm not sure I understand the protocols. Can someone aide me?

When I get an email where the message itself has a single '.' on a line this is
interpreted as the end of the email and everything gets truncated from there.
I especially get this from postfix mailing list were everyone is posting weird
email conditions...

Since I'm not able to read in everything perfectly according to the spec (eg:
<CRLF>.<CRLF>) I've been looking for a string that matches /^\.\r\n$/ which is
what the mail RFC says to do (Section 4.1.1.4).

Now, I find in 4.5.2 Transparency a statement about adding an additional '.' to
the client sending an email.
- Before sending a line of mail text, the SMTP client checks the
first character of the line. If it is a period, one additional
period is inserted at the beginning of the line.

But if this was always the case, then the client (being postfix) would include a
'..' and not '.' and all would be well. But that's not what I'm seeing.

Do I understand this correctly that, as a content_filter of postfix, I should
always see only one /^\.r\n$/ and at that point can consider the message content
complete and proceed with delivery?
And if I see '..' then it's not a match to /^\.\r\n$/ and should not have a
problem with it?

I don't believe I can wait until QUIT as this disallows ESMTP from working.