exchange server 5.5 problem.

My problem is I can’t get my email from out sid (they still on the server of the provider),they can’t reach my server,and also the mails of my clients in my network just qued in exchang server and does’t send to out sid in spit of that I have connction Dialup .I can internet through the server,I can ping the server of my provider.What is wrong help plaese