Hi Hurricane,

Thanks for the beers! Much appreciated as always!

If they are truly getting unsubscribed then before the subscription row is deleted from mp_LetterSubscribe table it is logged into the mp_LetterSubscribeHx table for history of the unsubscribe activity. But there is currently nothing in the UI to view that data so you would have to access the database directly.

Another thing to understand about newsletter subscriptions is if an anonymous user (ie not logged into the site and possibly not even yet a site member) subscribes via the Newsletter Sign Up Module then a verification email is sent to the address to activate the subscription. If they never click the link then they don't get verified and newsletter is only sent to verified subscriptions. So an email could be in the list but not verified and therefore no mail is sent to it. However site members who sign up while logged in are considered already verified.

Another thing to consider is whether the message is getting blocked by spam filters or landing in the spam inbox without being noticed by the subscriber. It is getting more and more difficult these days to send any kind of bulk email without getting flagged as spam and users may just think they are not getting the newsletter but it is landing in the spam box. Recently gmail was blocking all of the forum notifications sent from this site or if not blocking it was flagging it as spam even though it was valid subscribers to the forums.

Hope that helps,

Joe