We have a single Exchange 2003 server and I applied an updated Cert for the server for webmail and the activesync.
After I updated this, the webmail works fine, but the active sync for the phones have stopped working.
I tried to setup a new phone and get
There are problems with the security certificate for this site.
Certificate not from a trusted authority.
It was just a renewal of the cert and the webmail doesn't show any issue.