Non-standard headers

[Ned Freed]

> I recently downloaded a message from one of the servers on the WWW supposed
> to provide mime-compliant e-mail for the purpose (presumably) of testing
> mailers and configurations.

> This e-mail included header lines such as:

> MIME-version: 1.0
> X-Mailer: EmailTest (Viewer Test Page Email Test)
> Content-type: image/gif
> Content-transfer-encoding: base64
> Encoding: 90 base64
> Content-Name: a_bitmap.gif

> Now I wonder about those last two lines. I don't see any mention of such
> beasts in RFCs 1521 or 1522. Shouldn't they be X- headers?

No, they don't have to be X- fields. There's nothing to stop someone
from using any field name they like in an RFC822 header. The only
restrictions are on how standardized fields are used.

> If not, and in fact they are legal, where are these header lines described?

I suggest that you look at RFC1154/RFC1505 for a suggestion on what the first
of these fields probably "means". (The quotes are there because these RFCs are
not standards and have no more weight than casual use of some other sort.
The use of a MIME encoding in this context is not mentioned, but the
general idea behind the header is there.

The second field seems fairly obvious to me -- its the file name.

> In fact, putting in a much broader plea, isn't there somewhere (someone want
> to write an RFC??) that pulls together all the recognized headers into a
> single document, with pointers to where they are discussed in detail? There
> are several headers in common use that I've never seen written up anywhere.

There are a couple of drafts floating around (including one I wrote) but
nothing has made it all the way into RFC form. Not yet at least. Its a
huge amount of work, as I'm sure you must realize.

Ned