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TvxTLSType

TvxTLSType = (fttNoTLSSupport, fttImplicitTLS, fttUseRequireTLS, fttUseExplicitTLS)

Example​

procedure RequireExplicitTLS(var Mode: TvxTLSType);
begin
  Mode := fttUseRequireTLS;
end;

Usage​

TvxTLSType controls whether a transport uses no TLS, implicit TLS or an optional or required explicit TLS upgrade.

Members​

ValueOrdinalMeaning
fttNoTLSSupport0Do not use or request TLS.
fttImplicitTLS1Start TLS immediately on the implicit-TLS service/port.
fttUseRequireTLS2Use an explicit TLS upgrade and fail if the server cannot provide it.
fttUseExplicitTLS3Attempt an explicit TLS upgrade when available; the Velox policy can continue without it when unavailable.

Behavior and boundaries​

  • fttUseExplicitTLS is opportunistic and can permit a plaintext connection if the upgrade is not offered. Use fttUseRequireTLS when confidentiality/authentication is mandatory.
  • Implicit and explicit TLS normally use different service ports and server configurations. Selecting the wrong mode commonly causes handshake or protocol errors.
  • fttNoTLSSupport and opportunistic fallback must never carry credentials or sensitive payloads over an untrusted network.
  • TLS policy does not select the protocol version, validate certificates or configure authentication. Combine it with a secure SSL client mapping and certificate/hostname verification.
  • STARTTLS-style upgrades can be stripped by an active attacker unless the client requires the upgrade. Log and fail closed on a required-mode negotiation failure.
  • The same enum is reused by different Velox protocols; exact command sequencing and defaults come from the transport.

Additional Technical Info​

TvxTLSType maps directly to Indy's TIdUseTLS policy for mail and other TLS-upgradable protocols. It answers when and whether TLS is required; TvxSSLClientType separately selects the SSL/TLS protocol mapping.

Implicit TLS starts encryption as soon as the connection opens. Explicit modes connect in plaintext and request a protocol-specific upgrade such as STARTTLS.

Related Code Library entries

External references

Created 2026-07-15