How to install the message was undeliverable. All servers failed to receive the message

Error Source: jmail. Message
Error Description: the message was undeliverable. All servers failed to receive the message

Possible causes:

1. user name and password
InCodeTo write

MSG .. mailserverusername = "username"
MSG. mailserverpassword = "password"
Or

MSG. Send ("User name: password @ server.net ")
The username and password of the email server to which the sender connects. The user name and password must exist on the server and be correct. It seems that the username and password should not be underlined.

2. the firewall blocks network communication or network faults
It is possible that the firewall will think this is a worm-caused mass mailing situation, so it will prohibit mass mailing.
Therefore, you may find the firewall settings.

3. The jmail component has insufficient permissions.

4. email server fault