Level: Intermediate
Transport Layer Security encrypts the connection between mail servers during transmission, and its presence or absence is increasingly factored into deliverability decisions.
TLS Protects the Connection, Not Just the Message
Opportunistic TLS encrypts the SMTP connection between sending and receiving servers, protecting message content from interception during transit across the internet.
Most Modern Mail Servers Support TLS by Default
Current mail server software generally negotiates TLS automatically when both sides support it, though verifying this is actually happening for your specific sending infrastructure is worth confirming directly.
Lack of TLS Support Is Increasingly Treated as a Red Flag
As TLS has become a baseline expectation, a sending server that can't or doesn't negotiate an encrypted connection is increasingly viewed with suspicion by security-conscious receiving systems.
Next step: Use the Server Status Checker to check your sending server's current configuration to confirm TLS is properly enabled and functioning.