You can always go look at the Phoenyx to make sure there's nothing
you're missing (and the on-web reading is functional, if a bit Spartan
so far... I use it myself):
As a general rule, the Phoenyx is very good about mail delivery, though
there's nothing we can do about silent discarding at the recipient's
end (which is way too common these days).
With the beta software, though, I won't rule out the possibility we
have a bug here and there, at our end.