The most common protocol (method) for sending mail on the Internet is called SMTP. One of the disadvantages of SMTP is that it has no support for authentication of the user. In other words, the protocol has no way of making sure that the users who are trying to send email actually are who they say they are.

Because of this, the SMTP protocol can be exploited to send unsolicitied junk email ('spam'). People could 'get into' any machine and send hundreds or thousands of email messages without ever logging in. This is called 'relaying.' Service providers such as ENoor have had to come up with a way to authenticate the users to prevent this from happening.

If you get a message that indicates that the connection to the mail server failed, but you are able to access the Internet, then your ISP is probably blocking you from all SMTP servers except their own. This is so that if they ever need to know who sent out a particular email, they can trace it back to the appropriate user account. The thing to do in this case is to change your SMTP server to that of your ISP. Contact your ISP for the SMTP server that you should use.