[curt.clifton]

Some quick Googling shows that Thunderbird is at least somewhat AppleScript-able. An interested person with AppleScript skills could likely put something together. The only question would be whether there is someone who satisfies all the criteria: Thunderbird user, OmniFocus user AppleScript programmer, and willing to share.

Over on the OmniFocus Extras forum is a thread where people can request scripts. Perhaps a post there is in order?