Google Message Security for Google Apps Administration Guide - Manual (Page 318)

318 Message Security for Google Apps Administration Guide
This message is an automated alert from your email security
service.
The email security service was unable to accept messages from the
following domain, because the domain's mail server did not
establish a TLS connection:
Your Inbound TLS by Domain encryption policy requires messages from
this domain be sent using TLS. Your email security service defers
messages if the domain's mail server does not establish a TLS
connection with the service.
Recommended action: Contact the email administrator for the domain
.
If the problem cannot be resolved, you can use the email security
service's Administration Console to delete the encryption policy.
This will allow email from this domain to be received, but without
encryption.
If you see this message, the sender tried to send you a message buy couldn’t
establish a TLS connection. Contact the sender to troubleshoot TLS problems, or
disable Police Enforced TLS if you do not wish to continue requiring TLS
connections from the sender.
Inbound Mail (Local)
When Policy Enforced TLS blocks an inbound message because the email
protection service could not establish a connection with Google Apps Mail, your
administrator will see the following alert:
This message is an automated alert from your email security
service.
The email security service was unable to accept messages from the
following domain, because a TLS connection could not be established
to your mail server:
Your Inbound TLS by Domain encryption policy requires messages from
this domain be sent using TLS. Your email security service defers
messages from the domain when either the domain's mail server
cannot establish a TLS connection with the service, or the service
cannot establish a TLS connection with you.
Recommended action: Verify that your inbound mail server supports
TLS connections. Then check your TLS settings in the email security
service's Administration Console.
This alert message is very rare, and indicates a problem establishing a TLS
session between the email protection service and Google Apps Mail. If you
receive this message, check your Google Apps Mail server, or contact Google
Apps support to troubleshoot the problem.