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Re: fun with header syntax

1991-07-09 16:17:48
In article <9107092144(_dot_)AA20025(_at_)dimacs(_dot_)rutgers(_dot_)edu> you 

1. How many people have noticed that it appears to be perfectly legal for
an RFC822 message to contain more than one Message-ID header?

2. What fraction of software that is cognizant of message IDs will actually
deal with this correctly (at a minimum, without dumping core!)?

  Apart from news, there is probably not a lot of software that deals
with message IDs at all, although some mail UA software uses it for
an 'In-Reply-To:' header.  It looks as if 'sendmail' will just log each
such Message-ID, while I believe mail2news will just use the first.

  I suspect a far higher proportion of software will be confused by a
'From:' header which has two or more addresses, although this is explicitely
allowed if 'Sender:' is present.

3. Is this considered desirable, or is it worth fixing in the 822 revision?

  It is probably not desirable.  But it is arguably not broken, so not in
need of fixing.  How much software deals with 'Resent-Message-ID:'?

As you might expect, this came up in dealing with Yet Another Pathological
News Article which landed on 822's doorstep by way of 1036.  It can, and
probably will, be dealt with in the forthcoming 1036 revision as far as
news goes, but it was enough of a surprise to me that I thought it might
be worth raising in the 822 context.

  In news, message-id is right up front as one of the most important headers.
But with mail it is far less important, perhaps because of all those mailers
which emit mail without a message-id in the first place, not to mention those
mailing list processors which strip out existing message-id headers.

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