It's like stuffing envelopes. If you have to do 3 or 10 inefficiency doesn't matter that much. If you have to do 100 or 500 or 5000 all that extra time to guess

It's like stuffing envelopes. If you have to do 3 or 10 inefficiency doesn't matter that much. If you have to do 100 or 500 or 5000 all that extra time to guess name@ or name.last@ or nlast@ or n.last@ etc. is a big time waste. Paving to have the right address (even if some aren't correct because they've changed) is worth paying for.