Unverified50% confidenceFactExact time
STARTTLS initiates an upgrade request within an SMTP session to switch a plaintext connection to a TLS encrypted channel, rather than encrypting as soon as the connection is established.
1
Sources
50%
Confidence
Long-term
Relevance
11/1/2026
First Seen
Sources
Related Entities
Related Claims
UnverifiedSTARTTLS has an opportunistic encryption problem: a man-in-the-middle stripping the STARTTLS directive causes communication to silently downgrade to plaintext transmission.71% similarVerifiedTLS encryption, on which HTTPS relies, only protects the transmission channel between two communication endpoints; in a relay proxy model, the relay server is the TLS session endpoint and can read plaintext request content after completing TLS termination.70% similarVerifiedAn HTTPS man-in-the-middle proxy tool completes the TLS handshake with the app using its own certificate, while simultaneously establishing a separate TLS connection with the server using the server's real certificate, enabling decryption and re-encryption of encrypted traffic.67% similarUnverifiedCompared to TLS 1.2, TLS 1.3 simplifies the handshake process (reducing from 2-RTT to 1-RTT), removes insecure cipher suites, and enables forward secrecy by default66% similarUnverifiedSTARTTLS is opportunistic encryption that falls back to plaintext transmission if the peer server does not support it; MTA-STS and DANE attempt to address downgrade attacks but have limited adoption rates.65% similar
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