ietf-822
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Re: CRs in messages

2001-05-22 09:33:18
Is it our MTA which is incorrect by interpreting <CR>.<CR> as the same as
<CR><LF>.<CR><LF>
or is it the sending MTA/MUA which is incorrect by creating a message with
<CR>s in it and then not padding the '.'. (Surely if it really wants <CR>
characters rather than <CR><LF> line terminators, it should use
Quoted-Printable or Base64 encoding, not just put them in there as ASCII
0x0d characters)

your MTA is making a too-liberal application of the "be liberal in what you
accept" principle.  unfortunately there used to be a lot of MTAs (mostly
misconfigured sendmails) that would send <LF>.<LF> (not sure about <CR>.<CR>)
rather than <CR><LF>.<CR><LF>, to terminate the message.  many MTAs adapted
by accepting any of  <CR> <LF> or <CR><LF> as line terminators.

I still see <LF>.<LF> on occasion; it used to be extremely common. I've only
seen <CR>.<CR> a couple of times, I think it originated from some fairly
obscure Mac mail systems. I suspect <CR>.<CR> is dead at this point, but of
course there's no way ever to be sure about this stuff.

the sending MUA probably shouldn't be putting bare <CR>s in the message 
either.
however, this is perfectly legal in RFC 822.

But not legal MIME. See RFC 2045, sections 2.7 and 2.8. And while it is true
that MIME is intentionally constructed to be subset of what's allowed by RFC
822, violating it in this way isn't a good idea, regardless of whether or not
you're sending MIME messages.

                                Ned

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