The MIME type specified in Content-Type header is ignored and the extension is used to determine the MIME type. For instance, an attachment of text/plain type with the extension '.diff' or '.patch' is not recognized as a plain text document. When I open it, Mozilla prompts me to select a program to open it with or to save to a file. Content-Type: TEXT/PLAIN; charset=US-ASCII; name="test.patch" Content-Transfer-Encoding: BASE64 Content-Description: test Content-Disposition: attachment; filename="txt.patch"

I may have to change the summary line. When I try to open a 'text/plain' type file with an unusual extension (.e.g. patch, or diff), Mozilla does recognize the file type correctly as 'text/plain'. What's very odd is that the dialog box pops up, in which Mozilla says that The file "txt.diff.txt" (the original name is txt.diff) is of type text/plain (Text File), and Mozilla does not know how to handle this file type. This file is located at: imap://........... What should Mozilla do .... I'm not sure I've seen this behavior on Linux. I'll change platform to all if I have a similar problem on Linux.

I think that this is the correct (and this bug invalid) because of this : Content-Disposition: attachment; filename="txt.patch" The "attachment" forces Mozilla to display the helper app dialog.. (bz would know the answer but he doesn't read bugmail... )

and Mozilla wnats to save "txt.diff.txt" is correct because it's a text-File and many helper fails if you try to open a text-file with other extensions. I think this is a dupe of bug 185618. Mozilla would display it if you add a "Inline" into the header : Content-Disposition: inline; filename="test.diff" *** This bug has been marked as a duplicate of 185618 ***

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