Save method will save the message (or the message part,
depends on where do you call it from) to separate file. You
can use Save method only if you have retrieved full message
from the server, not only the headers.
Saving a message sometimes can be time consuming
process. Sometimes is a better idea to set Message.Filename property to
destination file prior to downloading message - in which
case message will be saved there directly during retrieval.
wodPop3 will not delete that file in that case.