The same thing was happening to me last week. When, for instance, there were ten new posts in a thread on the "Ships" forum (those who inhabit it know what thread I'm talking about), I'd get thirty e-mails from FSM. One evening the total was in the neighborhood of fifty.
Whatever the problem was - and wherever it originated - it seems to have gotten fixed. For the past few days I've only been getting one copy of each notice.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.