You could register something like "Cair.X" which is 6 characters long, and
then you can use "CairX" in your emails because Gmail ignores periods within
the account username when it is receiving emails. (I'm pretty sure you can
do this ... haven't actually verified it with a 5-letter username.) I think
you can set it up to send them that way too. Within the headers that
normally aren't displayed, there will be lines with "Cair.X" in them, but
most people (except Microsoft Outlook users) wouldn't see them.
Andy