Things seem to have calmed down. I'm constantly monitoring incoming email queue cloggage in the one region where this was a problem before Xmas. Since then I've had one server clog up but the rest of them are fine.
it just makes no sense why there'd suddenly be this big spike in clogging after years of relatively smooth sailing then it goes away mostly. Who knows when it will strike again. I sure feel better knowing for sure whether they are all unclogged or not. Next time you whip up a simple email based server you should add in a little "ping" type handler so later you can make a little email server poller to check your servers if that becomes a problem for you too.