I don't know if this has been discussed before or not, but wanted to get this out there for anyone else who may encounter this problem. I just received a couple Droid 3's into the office and could not get our corporate email accounts to setup on the phone, kept receiving an "Unable to connect to server" error message. Turns out, the problem is the security certificate on the Exchange server is a self-assigned certificate, and therefore the phone would drop the connection since the certificate isn't digitally signed. After spending about an hour and a half on the phone with Verizon and Motorola tech support, the following work around was finally giving to me and worked (this should also work if the certificate has expired):
1. Go to setup a new corporate sync account.
2. For email address, enter your gmail address.
3. For password, enter your gmail password.
4. For username, enter your gmail address again.
5. Tap Next
6. You will get an error message saying "Could not auto-detect server." Press OK.
7. For server, enter m.google.com
8. Tap Next.
Your gmail account should now be setup as your Corporate Sync account. Now you can go in (Home Screen -> Menu-> Settings -> Accounts) and edit the information for the Corporate Sync account to your actual corporate account. Make sure you uncheck the box for "Verify Certificate."
1. Go to setup a new corporate sync account.
2. For email address, enter your gmail address.
3. For password, enter your gmail password.
4. For username, enter your gmail address again.
5. Tap Next
6. You will get an error message saying "Could not auto-detect server." Press OK.
7. For server, enter m.google.com
8. Tap Next.
Your gmail account should now be setup as your Corporate Sync account. Now you can go in (Home Screen -> Menu-> Settings -> Accounts) and edit the information for the Corporate Sync account to your actual corporate account. Make sure you uncheck the box for "Verify Certificate."