When somebody changes their email address, you only have to edit their entry in the address book, which you have to do anyway. If you used the nickname in Eudora filters and not their email address, the filters will continue to work without any editing (and searching the right filter for 15 minutes).
Filter on Nicknames in Eudora
If somebody adds a new email address with the old one still functional, you still need only add it to their nickname. All filters built with that nickname will now work on both the new and the old email address. You can, of course create a separate nickname for the new address ("andrea" with both addresses and "adrea_yahoo.com" for her Yahoo Mail address).
If you create a filter using a nickname in Eudora,
- make sure the criterion contains intersects nickname,
- followed by the nickname.
