"signing" email messages

This may sound like nit-picking, but it can be annoying. 

For those of you who have deployed certificates in your email clients, could you please *not* sign messages you send to this list? I have no reason to doubt who you are, nor do I have a reason to import your certificate into my store.

My email client is *somewhat* braindead, and prompts me twice for each message that is signed by an unknown certificate authority.

Thanks for thinking of this issue.