Just to reassure Johnny J, the Tuesday am SMG class HAS done a "confirm/opt in if you want to stay on the list". But as he says, many of us involved in clubs, classes, etc will hold current and older lists, complicated by the fact that many of the people on the lists are personal friends, and you may have known them and had their email address long before any list was set up, so where do you draw the line? Can you remember how you acquired every email address in your contacts - as a personal one, or to go on a list?
As for my list of 200, that refers to events that we organise two or three times a year, so I can't just delete them all and start again. Those who are on it gave their e-addresses voluntarily. Rarely, if ever, has anyone asked to come off the list, although that option has been written into previous emails sent.