Not as readable, but each inter-character spot is a bit, and if you have 11 bits, you can represent 2^11 addresses.

EDIT: Assumes Zero or One periods per bit-gap; if you can chain them, the sky’s the limit.

I never understood why that was useful. If you're a spammer that harvests email address or if you're an unscrupulous service that sells your user email address to spammers, wouldn't you simply remove the '+' suffix from any gmail address before commencing your spamming?