POP3MessageInfo is used to return information about messages stored on a POP3 server. Its fields are used to mean slightly different things depending on the information being returned.
In response to a status command, number contains the number of messages in the mailbox, size contains the size of the mailbox in bytes, and identifier is null.
In response to a message listings, number contains the message number, size contains the size of the message in bytes, and identifier is null.
In response to unique identifier listings, number contains the message number, size is undefined, and identifier contains the message's unique identifier.
@author Daniel F. Savarese