I received notification that a subscriber had been dropped from my mailing list today due to a "user not found" error. My error monitoring is set up to drop subscribers after 100 errors or errors for 4 days. The only problem is that no previous errors for this user had been reported. Today's notification was the first indication that there was any problem with this particular user. The user has his option set for non-digest mode. The mailing list has handled about 35 messages during each of the past 4 days. The only possible explanation that I can see is that, for some reason, perhaps his ISP returned multiple error messages for each undelivered mail message yesterday. This seems so unlikely that I wonder if anyone can provide any other reason why the user was dropped so suddenly by the error monitoring system. And what do I tell this user if he asks why he was dropped? Les