I don't think registering an alias in this situation is a good idea. There will be folks who have [log in to unmask] who don't have [log in to unmask] accounts. There are several sources of conflict and consternation waiting to happen. I've seen it here (a long time ago). Maybe having customer (or list-manager) issue an appropriate CHANGE command (or some site-administered RYO-script) would be better? YMMV /Pete