Hi Steve and Dean,
Thanks for your replies.
I don't think the people whose records were deleted unsubscribed from the list.
What I'll test will be to increase the bounce settings to 4 bounces in 30 days and see if folks on the list still get deleted. Realize that some other bounced messages happen because of full mailboxes, and worse yet email addresses which were entered incorrectly (e.g. janedoe@yahoo.cm instead of yahoo.com) when they signed up.
Thanks again.
Cheers
tony