The BearerToken property specifies the OAuth 2.0 bearer token
used to authenticate the user. This property is used as the default
value for the Authenticate method if the token is
not provided as an parameter.
Assigning a value to this property will change the current
authentication method to use OAuth 2.0 if necessary.
You should only use an OAuth 2.0 authentication method if you understand
the process of how to request the access token. Obtaining an bearer token
requires registering your application with the mail service provider
(e.g.: Microsoft or Google), getting a unique client ID associated with
your application and then requesting the token using the appropriate
scope for the service. Obtaining the initial token will typically involve
interactive confirmation on the part of the user, requiring they grant
permission to your application to access their mail account.
Your application should not store an OAuth 2.0 bearer token for later
use. They have a relatively short lifespan, typically about an hour, and
are designed to be used with that session. You should specify offline
access as part of the OAuth 2.0 scope if necessary and store the refresh
token provided by the service. The refresh token has a much longer
validity period and can be used to obtain a new bearer token when needed.
If the current authentication method does not use OAuth 2.0, this
property will return an empty string and you should check the
value of the Password property to obtain the
current user's password. Refer to the AuthType
property for more information on the available authentication methods.