Add method will create new instance of Pop3Message object,
add it to collection of all messages, and return reference
to that object. This method should be used in Connected
event, because adding messages (or removing them) later
during session is not allowed by Pop3 protocol
specification.
If Filename argument isn't specified, new object
that is created will contain no message. This means that if
you don't fill it up using Body property,
user will see this message listed, but it will be
zero-sized, and may cause problems with some clients.
You can ignore object returned by this method, because
you can access it later through Messages
collection. However, if there's any data you need to
store in this object, you should store returned reference
locally and use it.
If you specify Filename parameter, be sure that file on
disk contains only one message. If this is not the case, if
that file actually represents mailbox with few messages,
use StartPosition
and EndPosition
properties to specify location of the message in mailbox
file.