whitelist advice

[Alan Fiebig]

In the never ending quest to balance stopping spam and keeping customers happy with minimum false positives, I am considering adding a whitelist rule of:
  "From   @*.org  no"

to allow all mail sent from '.org' site.

1) How much risk do any of you think I'd be running? Have any of you seen much spam sent from '.orgs'?

2) Is that the correct format? I've seen rules created with '*@xxx.xxx' and with just '@xxx.xxx'. Is the astrix wildcard really required in front of the '@' sign?

-Alan