Comment 14 for bug 303140

(In reply to comment #13)
The "Detach..." and "Delete" features exist in SeaMonkey, but as of version 1.0.2 they are useless for messages that are signed or encrypted (or both). Detaching (which allows saving the attachment) or deleting the attachment altogether breaks the signature and removes the entire content of the message body.

The original idea behind the bug—which is to preserve the content of the message while deleting the bulky, unnecessary attachments—is completely ignored by the current implementation. You can either save the whole signed and/or encrypted message with the attachment, or you can "detach" everything from the message (but "detach" really means delete everything from the message...signature, attachment, and message body content -- everything is lost) except the header.

Hence, for signed and/or encrypted messages the feature is utterly useless as a means of saving the message but deleting only the bulky attachment.

BTW, I notice that there are still only two votes for this bug -- yours and mine. (sigh)