Indicates if the server has specified a capability.
True if the named capability is found in the list
If the EHLO command succeeds, the SMTP server returns a list of optional capabilities that it supports.
The SmtpClient class saves this list of capabilities
and provides methods that allow you to examine it. The
HasCapability method provides a simple way for you to check
if the server supports a particular capability. Internally, the
HasCapability method iterates over the list of capabilities
attempting to match the desired capability name. The method
returns a true value if it finds a match.
SmtpClient Class | Hunny.Mail Namespace