When I send multiple entries, I do it in separate messages sent from the same email address and with the same postal address. In the past, I've also sent multiple entries in a single email with the pseudonym alongside my real name. That seems to work, too. Lucy doesn't seem to be much of a stickler about such things.
I haven't tried multiple entries with Tessa (except that when the toast comp got repeated I resubmitted the previous year's entry along with a new poem. Tessa apparently didn't care for either).
P.S.: It's Noam D. Plum. Plume would be silly.