Office communicator 2007 or 2007 R2 may come up with the error “there was a problem verifying the certificate from server. Please contact your system administrator”.
Usually when connecting to office communicator server trough the local network there shouldn’t be any problem as all ports inbound are opened. The problem occur when start accessing the office communicator server from a different network. In this way most networks are protected behind a firewall so most of the ports (accept 80) are blocked so that the office communicator client may experience some difficulties to access.
To manually configure DNS names and ports to office communicator client do the follow:
1. Open office communicator client.
2. Go to “tools” < “options”
3. At the left pane you should “personal” < fill in the “sign in address” on that tab
4. Click “advanced” button on the right < check the “manual configuration”
5. If connecting only through local network then fill in the DNS name or IP address of the internal server.
If connecting trough a far network then fill in the external server.

The connection problem which pops the error: “there was a problem verifying the certificate from server. Please contact your system administrator” usually indicates a problem in the certificate (if the certificate is expires) or a firewall issue (for example when a SSL limit is enabled and the sessions reach the limit).
If SSL port is opened you can test the connection using Telnet command as follow:

  1. Go to Start < run <type “CMD” < press “Ok”
  2. On the command prompt type < telnet OCS_Server_DNS_Name SSL port, so basically if we need to check connection for example to server: OCS.mydomain.com the appropriate telnet command will be:
    Telnet OCS.mydomain.com 443
  3. Indication – connection refuse points to problem in the server side, otherwise connection established and ports open to work with OCS.

There is a way to work around this problem by installing the certificated located on the server to the local windows XP or windows 7 machine.
Simply exports the .cer file located on the server and imports it to windows XP or windows 7 as follow:

  1. Go to start < run < type “MMC” < press “Ok”
  2. Go to “file” < “add\remove snap in”
  3. Press “Add” < add the “certificates” snap in.
  4. Choose the “computer account” when asked and press “finish”
  5. On the console root < expand the “Certificates (local computer)”
  6. Right click “personal” < point to “all tasks” < select “import”
  7. Press “next” for the first screen < browse for the .cer file exported from the server < press “next” to end the procedure.
  8. You should now see the certificate marked on the certificates tab with appropriate server name on the “issued to” menu.
  9. Try now to connect to OCS server.