WhiteList

WhiteList will generate a list of all people you have mailed with. This list is usually called a whitelist for e-mail spam, as those are real people.

You can export that list as v-cards so you can add them to a group in your address book

WhiteList creates a list of all people in in your mails. It's ordered by the number of mails you have sent and received by that person.
You can export the list of people to a v-card file. When you upload that file to your mail providers mailbox, your mail provider then has a better idea which e-mails to accept.
Only the E-Mail address is exported by default. That way your e-mail provider does not get more information that it needs to.