There are a variety of reasons email does not arrive;
a) it's simply filtered out somewhere along the line. Usually it's best to test with a local server, one you control, to determine what is the "sending side" and what is the "server side".
b) Some servers require, or prefer, you to log on before _sending_ mail. The send mail object has properties for this, if you have them, and your server will accept them, then it's a good idea to send them.
When in doubt use the _trace method to send the conversation between the client and the server to debugview. Adding calls to ._trace in the SEND and PROCESS methods in the SendEmail object is the way to do this.
cheers
Bruce