Installation JMail appears the message is undeliverable. All servers failed to receive the message solution _ Application Tips

Error Source: JMail. Message
Description of error: The message was undeliverable. All servers failed to receive the message

Possible causes of the problem:

1, user name and password
Write in the code.

Msg.. Mailserverusername= "User Name"
Msg. mailserverpassword= "Password"
Or

Msg. Send ("Username: password @server.net")
The mail server to write the sender-side connection and the username and password to enter the mail server. The username and password must be present on the server and correct. And it's as if the username and password are best not underlined.

2. Firewall blocks network communication or network failure
It is possible that the firewall will think this is the worm caused by the mad message, so it will prohibit mass mail.
So check your firewall settings and you'll probably find out.

3.jmail Component Not enough permissions

4. Mail server failure