Thanks, everyone, for the help. Stan's advice that these "are probably not worth obsessing about" is definitely worth listening to! :-> Regarding Bill's comment: > On many systems, a maximum message size can be defined. I beleive Hotmail > is about 1.5 MB. At least one of the bouncing messages was less than 30k, so I've come to believe Microsoft uses 5.2.3 to mean they have disabled the account by setting the quota to zero. peter