The whitelists have priority over the blacklists, so if you whitelist *@sbcglobal.net, that will allow all emails from that domain to become unfiltered, regardless of the entry in the blacklist.

However....

The whitelist (as most other list) supports the use of RegEx (Regular Expressions). You could create a single keyword using RegEx that will cause a match for all addresses except the "abcd@sbcglobal.net".

RegEx is very very powerful but also a bit "challenging" to create more complex rules. We'll try to come up with an expression for yo within the next few hours. In the meantime if there are any RegEx gurus reading (and there are quite a few excellent RegEx masters who use SpamFilter!) suggestions are welcome!