> Date: Sat, 31 Oct 1998 08:32:50 -0800
> From: Dan Smith <[log in to unmask]>
>
> I have managed to collect several addresses on the three lists that I
> manage that generate the following error mesage: "Last error: 553 5.1.1
> unknown or illegal user". These folks no longer show up when I "review" the
> lists and my attempts to "delete/quiet delete" them results in a message
> which essentially says that it can't be done because they are not members
> of the list.

This is typical when someone is subscribed using a forwarding service.
More correctly:
The user is subscribed using one address, which forwards the messages
to another address which generates the error message.
You may look for hints for the subscribed address by looking at header
fields of the message being bounced, e.g the "Received:" fields may tell
you the track where the message went through. "Resent-*:" fields may also
give you hint. You may "scan" your subscribers' list using parts of the
user name. It is not always easy to locate the exact subscription address.

Uzi