I had three keys that had userIDs matching one particular e-mail address. They
were stored in the tofu db's bindings table.
I deleted two of them (only one remained), and then i tried to encrypt mail to
that e-mail address. I got the tofu prompt asking me about all three keys.
This was confusing -- what were these mystery keys that were no longer in my
keyring? (it would have been more confusing if it had happened more than a few
hours after the deletion of those keys)