service stopped working

Hi,
Your service seems to have stopped working the way it should.
Im using it on approx 10 websites and on most of these the emails have stopped arriving at destination!
I got emails sent to Google Mail addresses which were being regarded as spam by google.
And now i got emails which are not arriving at all, not even in the spam.
This is an urgent problem i hope you can come back quickly to me with adequate support.
much appreciated.
Thierry