A class used to represent forward and reverse relay paths. The
SMTP MAIL command requires a reverse relay path while the SMTP RCPT
command requires a forward relay path. See RFC 821 for more details.
In general, you will not have to deal with relay paths.
Add a mail relay host to the relay path. Hosts are added left to
right. For example, the following will create the path
< @bar.com,@foo.com:foobar@foo.com >
path = new RelayPath("foobar@foo.com");
path.addRelay("bar.com");
path.addRelay("foo.com");
Parameters: hostname - The host to add to the relay path.