Secure Mail does not sync emails after upgrading to version 10.6.0

Emails are not syncing for users after the Secure Mail update to 10.6.0. We will see the following Socket errors in the logs: 2017-07-25T06:17:37.266-0400 AGTunneler INFO 4 -AGSocket connect:withPort: -AGSocket connect:withPort:: CallOriginalconnect errno = 36 - 'Operation now in progress', fd = ...