The OnRecipient event is generated immediately before a
message is sent to a recipient. When used in conjunction with the
OnProgress event, this event can be used to track the delivery
of a message to multiple recipients. If an error occurs during the
delivery of the message, the OnError event will fire.
The Address argument is a string which specifies the
recipient email address.
The Cancel argument determines whether or not the message
delivery is canceled for the specified recipient. Setting this
argument to a value of true causes the SendMessage method to
not deliver the message and continue on to the next recipient. The
default value for this argument is False, which indicates that the
message should be delivered.
Note that setting the Cancel argument to True is different
from using the Cancel method, which would cancel delivery of
the message to all subsequent recipients as well as the current
recipient specified by the Address argument.