|Unknown||0||The current context is unknown.|
|Dns||1||The current context is DNS.|
|Smtp||2||The current context is SMTP.|
|Pop3||3||The current context is POP3.|
|Imap||4||The current context is IMAP.|
|Ews||5||The current context is EWS (Exchange Web Services).|
This enumeration is mainly used as the type of Protocol property of many network-specific exceptions and events (such as ConnectedEventArgs.Protocol).
The value of such a property indicates the context in which the corresponding exception or event has occurred. This provides the developer with additional information on the exception or event.
For instance, the developer implementing sending mail via Smtp component can read this property in the exception handler in order to determine whether the exception was caused by SMTP connection error or by DNS/MX error (or even by POP3 error during POP-before-SMTP authentication).