This page describes how to enforce TLS and behavior from a Sentinel Messaging Sender and Recipient point of view. In both cases below, we do recommend that the filters created be for the recipient.
TLS Outbound
This is the Sentinel Messaging sender’s perspective.
Most customers will want to utilize TLS for outbound, to ensure a secure mail transport.
- By default, the Sentinel Messaging outbound relay will use opportunistic TLS for initial sending.
- If the recipient server is not accepting our TLS session, we will fallback to standard transport and deliver anyway.
If an outbound filter is created then the condition should be based on the recipient domain (not the Sentinel Messaging customer). The action should be ‘Nothing,’ and the secondary action can be:
- “Enforce completely secure SMTP delivery”
- The sender must have a valid certificate in place.
- The domain name using to send must match the exact same domain on the certificate, unless it is a wildcard certificate.
- If there is no certificate, we will not deliver the email.
- “Enforce only TLS on SMTP delivery”
- No certificate required. The downstream server simply needs to accept the traffic over TLS.
- If the downstream server does not accept TLS, we will not deliver the email.
TLS Inbound
This is the Sentinel Messaging recipient’s perspective.
This is to ensure that mail from the Sentinel Messaging environment to the customer’s mail server environment is over TLS. By default, we attempt this over TLS to begin with.
If an inbound filter is created then the condition should be based on the recipient (the Sentinel Messaging customer), the action should be ‘Nothing’ and the secondary action can be:
- “Enforce completely secure SMTP delivery”
- Same as above. Valid certificate with domains matching required, or we will not deliver.
- “Enforce only TLS on SMTP delivery”
- Also similar. No certificate required, but the server we are passing the mail off to needs to accept the TLS connection, or we will not deliver.
If you have questions regarding filters within Sentinel Messaging. Please email support@digitar.com for assistance.