Problems with autodiscover

Hi. Since a week ago I am having a problem with some mobile devices and all seems it's caused for autodiscover problems. It works perfectly internaly, but not externally. I have done all the tests on https://www.testexchangeconnectivity.com/ and I receive almost the same errors in all of them, bellow an example:

	ExRCA is testing Exchange ActiveSync.
	The Exchange ActiveSync test failed.
	Test Steps Attempting the Autodiscover and Exchange ActiveSync test (if requested). Testing of Autodiscover for Exchange ActiveSync failed. Test Steps Attempting each method of contacting the Autodiscover service. The Autodiscover service couldn't be contacted successfully by any method. Test Steps Attempting to test potential Autodiscover URL https://mydomain.com/AutoDiscover/AutoDiscover.xml Testing of this potential Autodiscover URL failed. Test Steps Attempting to resolve the host name uce.edu.do in DNS. The host name resolved successfully. Additional Details IP addresses returned: xxx.xxx.xxx.xxx Testing TCP port 443 on host mydomain.com to ensure it's listening and open. The port was opened successfully. Testing the SSL certificate to make sure it's valid. The certificate passed all validation requirements.

When I try to navigate to https://mydomain.com/AutoDiscover/AutoDiscover.xml I received an error on the browser that says that the security certificate of the server is revoked. The major problem is that Blackberry and some Android can receive emails, but not send. Iphone and iPad are good (they can receive and send emails without problems). What could I do to solve that problem as soon as possible?

Melvintt
MCTS, Windows Server 2008 R2: Network Infrastructure
MCTS, Windows Server 2008 R2: Active Directory, Configuring