Push emails (ActiveSync) suddenly not working on server 2003

Today a small business server 2003 was shut down unexpectedly (Simple electricity issue). After the server came up, the ActiveSync was no longer working. What I mean is that people who had their phones configured no longer received emails automatically by push. However the emails did sync, after going to the email app, and refreshing them.
So what's going on? Actually it's pretty simple for people that know where to look, unfortunately I forgot about the order of the things to check, and it took me a bit longer.
If you go to the Application log in Event Viewer, you will see the following error:

IP-based AUTD failed to initialize because the processing of notifications could not be setup.  Error code [0x80004005].  Verify that no other applications are currently bound to UDP port [2883], or try specifying a different port number.

Or this:

 IP-based AUTD failed to initialize.  Error code: [0x80004005].

So what's the solution?
Just restart the DNS Service. Everything was ok after that.

But, the problem may come back again. So here's the permanent solution, after reading more about that on this page, you may need to add the following ports as reserved in the registry:

• 1645-1646 - Used by IAS
• 1701-1701 - Used by L2TP
• 1812-1813 - Used by IAS
• 2883-2883 - Used by AUTD
• 4500-4500 - Used by IPSEC

Add this to the following registry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\ReservedPorts

Now restart the server to make sure everything is fine.

Hope it helped somebody.