Comment 7 for bug 1154004

If you're good with regexps, consider that

^from:.*[\s,<](?P<femail>[^\s,>]+@[^\s,>]+)(.|\n)*^sender:.*(?P=femail)

when searched in multiline and ignorecase as is done for header_filter_rules will match headers with a From: followed by a Sender: with the same address. Thus, putting the two regexps

^from:.*[\s,<](?P<femail>[^\s,>]+@[^\s,>]+)(.|\n)*^sender:.*(?P=femail)
^sender:.*[\s,<](?P<femail>[^\s,>]+@[^\s,>]+)(.|\n)*^from:.*(?P=femail)

 in a Privacy options... -> Spam filters -> header_filter_rules rule with action Accept will pass a message with a From: and Sender: with matching addresses in either order.

Then following this with a second rule with regexps

^from:(.|\n)*^sender:
^sender:(.|\n)*^from:

and action Hold will hold those remaining messages with both From: and Sender: in either order without matching addresses.

This could work, but a possibly better way to do it is with a custom handler <http://wiki.list.org/x/l4A9>.

In any case, I consider this 'bug' to not be anything that can be 'fixed' and thus, invalid. Perhaps there is a feature request lurking in here somewhere, but I don't know what or how generally useful it would be.