IMailServiceCheckCertificateRevocation Property

bool CheckCertificateRevocation { get; set; }

Property Value

Gets or sets whether connecting via SSL/TLS should check certificate revocation.

Normally, the value of this property should be set to true (the default) for security reasons, but there are times when it may be necessary to set it to false.

For example, most Certificate Authorities are probably pretty good at keeping their CRL and/or OCSP servers up 24/7, but occasionally they do go down or are otherwise unreachable due to other network problems between the client and the Certificate Authority. When this happens, it becomes impossible to check the revocation status of one or more of the certificates in the chain resulting in an SslHandshakeException being thrown in the Connect method. If this becomes a problem, it may become desirable to set CheckCertificateRevocation to false.

Reference