Thanks for all the reply’s on this, however although email is a large issue, it is not the only issue and therefore the reason why we are now looking to move.
we've also experienced issues with our web hosting and our internet feed provided by Synetrix.
we have actually gone through all the points stated above with opening and closing port 25 etc.
With port 25 open, we actually became blocked to AOL, MSN and Google, which was far worse as synetrix refuse to set up their server DNS correctly resulting in our external IP not resolving with certain vendors. a very large headache as you can imagine, everything set up correctly with FQDN on our 2007 Exchange, but blocked emails all over the place.
we also experience web page down time without prior notice, this is incredibly annoying, plus internet down time without prior notice. as a result we were not impressed.
we need someone more reliable and more professional to support our needs, especially in an emergency.