anchor: Even if he is sorting the addresses by hand, he has the option of doing the work in a completely different way Also, if the same mailing list is used more than once, or is used again with slight modification, he can sort once and do many mailings.
positive: He doesn't have to do the work in the same way.
negative: If he's sorting the addresses by hand, he doesn't have the luxury of being able to do the work differently.