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tls_verify — specify how to handle the remote presented certificate


TLS_Verify = "no|ca|host|optional"


**Configuration Change. ** Support for GNUTLS is available as of version 4.1 for SMTP reception and SMTP deliveries only.

If TLS is set to required or ifavailable and TLS is negotiated with the remote mail exchange, this option specifies how the remote presented certificate should be handled.

This option can be set to the following:

  • no – The certificate will not be checked. Given the number of self-signed certificates used on mail hosts, this setting is probably the most useful.

  • ca – The connection will only proceed if the certificate presented is signed by a valid certificate authority listed in the CA list specified by TLS_Ca.

  • host – In addition to requiring that the certificate be signed by a valid certificate authority, the common name presented in the certificate must either exactly match the domain or mail exchange to which we are connected. If this verification fails, delivery fails.

  • optional – Performs the same verification as the host setting but allows delivery if the verification fails.


For custom behavior create a C module that uses the outbound_smtp_tls_verify_callback and inbound_smtp_tls_verify_callback hooks.

The default value is no.


tls_verify is valid in the binding, binding_group, domain and global scopes.

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