I checked out mdadm --help, it is rather alarming in that it seems to say that it won't tell you if it isn't working due to a mail configuration issue
I've visited several sites but can't find a command to force mdadm --monitor to send a message. looks like the program /bin/e-smith/mdevent actually sends the notice WHERE?
mdevent from the command prompt just gives error messages, no email!
My casual investigation indicates that the admin email fowarding is NOT loaded on a default installation, you have to go and poke at it from the control panel, a very easy step to overlook!