I suspect, given how I had to OK your message to the list, that your mail server is setting "Sender= [log in to unmask]" (or "root@wherever") on outgoing mail. This causes your backbone updates to go out as if they were coming from ROOT rather than from LISTSERV, which causes the X-TBREG operation to fail. Bottom line is that this is broken behavior, at least as far as LISTSERV is concerned, and a quick read of RFC822 would seem to back this up. ("root" is not acting as an agent for "listserv", so it should not be the "Sender:".) Nathan