Is Address Book a filemaker pro database?
If so, you can use the Import Records tool to import from a tab, comma delimitted (text) or several other types of files. If you can get your mailing list into one of these file formats, then it's fairly easy from that point on.
I'd look up Import Records in the on line help, it has a lot of different options, and then experiment with a copy of your file (if you already have data in it), so a mistake on your part doesn't mess up your original copy.
No, the Address book I mean is the application called Address Book that comes with OSX and is the database that the e-mail application (mail) and the iphone (contacts) use.
Take a look at the VCF Export using XSL that exports FMP contact information into vCard format here:
It is near the bottom of the list.