Including extra headers in outgoing e-mail

Having recently had a disk crash, and lost amongst other things, all my 
outgoing e-mails for several weeks, I feel the need to make sure my 
outgoing e-mails are saved somewhere else.

I'm thinking of getting a gmail account, and BCCing all my outgoing 
messages to there.

I recall having seen a plugin for Eudora that allowed extra headers to 
be included in every outgoing message. Could someone please remind me 
what it is called, and if possible where to get it?

Thanks

David