Verizon Droid to Exchange "Host Unknown"

What version of Exchange server are you trying to connect to?
Also, what is the host name that you are entering?  It should be a Fully Qualified Domain Name such as mail.yourdomain.com which should resolve to the IP Address that your Exchange Server site behind.

2003

Host name I am entering is

Mail.corp.domain.com

Please have a read through my Exchange 2003 / Activesync article.  I don't imagine you will have access to your server to check / tweak settings, but if you run the tests and all passes okay, then there should not be any need to tweak the server.
https://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/A_1798-Exchange-2003-Activesync-Connection-Problems-FAQ.html
If the tests fail, please post the full expanded results.

Am I supposed to test the connectivity from my phone?

All I get from the phone is "Connectivity Test Failed"

The host could not be resolved in DNS.

I know the host name is correct as I have taken it directly from outlook installed on my lap top which works perfect.

You can test the connectivity from Internet Explorer.  Just visit the website https://testexchangeconnectivity.com, specify manual server settings and complete the test.
Any problems, please let me know.
Alan

ActiveSync has to be enabled on the server, and your IT department has to make sure that your user account on the server is set up for ActiveSync.

Also, you said that your Outlook connection to the exchange server is working fine, but I wanted to know if your computer has a VPN connection to the office, or if it works directly over the internet. It's possible that you have to connect to the VPN before you can connect to the exchange server.

One (or both) of the above issues would be the cause of your problems.

If you type in the hostname you are using for the droid with /exchange on the end (example https://mail.domain.com/exchange) do you get Outlook Weeb Access? I am just wondering if the host name you got from outlook is the internal server name.

When in the office on the network I am able to connect to exchange without attaching to the VPN (server is at HQ and I am remote)  When at home I have to attach to VPN to connect to exchange

Then you likely got the internal domain name of your exchange server. What you need is the internet domain name of the exchange server probably the same domain name that you use for Outlook Web Access (webmail). That would explain why the name could not be resolved for the server name on the droid.

Then you have to set up VPN on the Droid as well, and you should then be able to use ActiveSync when VPN is connected. Unfortunately, that will make push updated pretty unuseable. Every time you want to sync up to the server, you'll need to connect to the VPN first. You can probably keep the VPN connected all the time (if it lets you), but that's usually frowned upon since all the web traffic to your droid will be going through your office VPN connection.

I forgot to mention, the Droid has PPTP and L2TP VPN capabilities out of the box under Settings -> Wireless & Networks -> VPN Settings. But if your office uses Cisco VPN, things get more complicated. You'll need to root your Droid, then get a kernel that has the TUN module built in, and then install openVPN.

We do not use Cisco VPN client, I just attach via windows VPN client.

I am new to the Droid (obviously) and from your comments I am assuming this phone is not designed to act as an appliance behind the firewall as the Blackberrys typically do?

I attached to the VPN successfully, however I still received "host is unknown" error when attempting to connect to exchange...

Is you exchange server's webmail (owa) page available via the internet ? If so you can sync using that as the server name so you won't need VPN.

Have you run the Activesync test on the test site yet?
I don't see VPN being an issue we need to worry about yet.
The Droid uses Activesync which is a Protocol developed by Microsoft.  If the server is configured and working for Activesync, then you should be able to configure your phone, but the test on the site I linked to will tell me what is going on and then we can move forward to a solution for you rather than spending time on red herrings.

OK, then I'm going back to my original comment -- you have to talk to your IT department s and find out if ActiveSync is actually enabled for your account. Have you ever used it before (on a different device)? Where are you getting the server / domain settings that you are trying to use?

ExRCA is testing Exchange ActiveSync.
       The Exchange ActiveSync test failed.
       
      Test Steps
       
      Attempting to resolve the host name exmail.corp.company.com in DNS.
       The Host could not be resolved.
        Tell me more about this issue and how to resolve it
       
      Additional Details

Got internet address for server....worked!  Thanks!