OT? /dev/null 5.1.1 email

That's got the same failure mode - if I take a 30-second hit and can't reach
the first MX, then the link comes up before I try the last MX, I hit the "bad" one.
And since the link burp is at *my* end, you don't even know about it, unless
you hook it into a full BGP feed with Zebra or something and see AS1312's routes
flap (and even then, it's dicy - a very short burp may not cause the routes to
be withdrawn)....