Thanks! Looks a good idea. I presume that a welcome message isn't sent if there's a welcome file specified.

I was recently involved in a move of a 500-strong list, which had been almost inert, to Mercury. When I set up the list and the welcomes went out, I got the initial blizzard of vacation messages, angry "what are these messages"? messages, and so on. Is there any way that I can set up the list without welcome messages, send out a VERP probe, and after the deletions send out the welcome messages?

I've not tried this but I suppose you could leave the welcome file field blank when you setup the mailing list so there is no welcome file to send and then manually send a welcome after all has settled down and then set the welcome file to what you want.