ietf-822
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Re: Problem with MIME and line length in Subject headers

2002-11-11 08:08:55

At 13:52 +0100 02-11-11, Arnt Gulbrandsen wrote:
A standard that is widely either misunderstood or incorrectly implemented certainly has a problem. IMHO, in this case a textual clarification is the best way to deal with it.

RFC 2822 says:

There are two limits that this standard places on the number of characters in a line. Each line of characters MUST be no more than 998 characters, and SHOULD be no more than 78 characters, excluding the CRLF.

With 78 characters, and MIME encoding, this means that the actual allowable length of a subject line using non-ASCII characters is smaller at least 16, maybe more than 16 less than 78. Many people will then get their subjects broken.

Agreed. (For the last thousand messages in my inbox, I see that almost 10% of the subject fields are wrapped into multiple seventysome-character lines.)

By adding that an "=" sign at the end of a subject indicates a soft line break, in the same way as in Quoted-Printable, this can be solved. But this requires a change in the MIME standard for encoding of unstructured text in headers.

It also creates a large compatibility break, since there's software that treats _today's_ line breaks as soft, and even more than displays all nonwhitespace.

It sounds easier to get more people to implement today's soft line breaks (FWS) correctly than to invent a new soft line break and then get everyone to implement that.

--Arnt