Create new threads for email replies

Issue Summary

Hi,

I'm new to both Drupal and Listhandler so, first off, apologies if I've missed something. I'm using Listhandler to archive a Mailman mailing list. The problem I'm having is that when people reply to an email, they usually quote the entire original text, often before their signature. The result is that the forum thread becomes very cluttered and it's difficult to read the replies. It would (arguably) be better if all incoming emails created a new thread (thus following the model used by most email clients, rather than behaving like a traditional forum).

(I'm also having problems getting Comment Upload to work, which doesn't help!)

I've attached a patch which adds a configuration option to create new threads for all incoming emails, whether or not they are replies to existing threads. If others might find this useful too, maybe it could be included in the next release?

Cheers,
Ian