You can use this site to test exchange activesync connectivity
The site is an official Microsoft site specifically for testing Exchange installations and connectivity. The test will fail if you use a self-signed SSL certificate, in which case, you’ll need to check the “Ignore Trust for SSL” checkbox. On the ActiveSync test page, you are asked whether you wish to use Autodiscover to detect the settings or to manually specify server settings. Exchange 2003 does not have native autodiscover, so you will most likely need to choose the latter option and provide the server name.
If you are getting failures check the following:
Firstly, you need to make sure that you have Exchange Server 2003 Service Pack 2 Installed. To check if you have it installed, open up Exchange System Manager – Start, Programs, Microsoft Exchange, System Manager. Then expand Servers, Right-Click your server and choose Properties. This will display whether you have SP2 installed or not. If you do not have SP2 installed you can download it here – http://www.microsoft.com/downloads/details.aspx?FamilyID=535BEF85-3096-45F8-AA43-60F1F58B3C40&displaylang=en
If you are trying to make an iPhone work, then you can also download the free iPhone App ‘Activesync Tester’ and this should identify any problems with your configuration or you can click on the following link: https://store.accessmylan.com/main/diagnostic-tools
You also need to ensure that TCP Ports 443 is open and forwarded to your Exchange server. If you are not using SSL make sure port 80 is forwarded.