Exchange 2010 Edge subscription question

Yesterday we had an inbound email problem where nothing was being delivered and our scanners would not send email to our inboxes  but internal email to internal email worked just fine. I didnt spend much time on diagnosing this I seen an event in the logs on one of the CAS servers.

Failed to connect to the Edge Transport server ADAM instance with exception The LDAP server is unavailable..  This could be caused by a failure to resolve the Edge Transport server name CTEDGEin DNS, a failure trying to connect to port 50636 on CTEDGE network connectivity issues, an invalid certificate, or an expired subscription.  Verify your network and server configuration.

CTEDGE is our forefront server. After I seen this I rebooted the forefront server without any further thought (which was a mistake) and inbound email and scanners starting working again. My boss seems to think that forefront has absolutely nothing to do with the problem.

If CTEDGE is our edge subscription does this mean ALL email in and out is going through that server before it hits the mailboxes on the cas servers despite the fact we have send connectors that are going directly to our mimecast (external) email filter?