[exim] Making Exim really fast

I don't know how many of you have tried SSD drives but they are really
fast. If you get a small SSD drive and run /var/spool/exim on it you'll
see a significant speed jump. If you do raid 0 it's even faster. Also if
you use a fallback host to do your retries of email that doesn't get
delivered on the first attempt you can keep the queue very small. And
SSD makes good high speed swap space.

My 2 cents ....