My email does not work

This can be any one of the following symptoms:
My mail client is reporting problems with authentication or rtcp hosts.
Sending of test mail in Outlook or Outlook Express fails.

Please check that your email client is setup correctly by using the following details:

POP3 server: mail. (eg mail.example.com.au)
SMTP server: mail. (eg mail.example.com.au)
Username: username@ (eg joe@example.com.au)

VERY IMPORTANT!
Also make sure that you have enabled authentication for the outgoing mail server (SMTP server). This option is labelled differently for various mail clients. A partial list is below:
Outlook and Outlook Express: "My server requires authentication"
Thunderbird: "Use name and password"

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Please check the above before proceeding

Optus and Bigpond are known to block port 25 which is necessary for sending mail through Horizon Hosting.
Please refer to the following two URLs describing the issue.
For Optus users
http://www.optusnet.com.au/help/dsl/faqs/email#port25
For BigPond users
http://bigpond.custhelp.com/cgi-bin/bigpond.cfg/php/enduser/stdadp.php?pfaqid=5562

There are two solutions to this problem. The first and easiest is to use Optus/Bigpond's SMTP servers to relay your mail through. Simply set the SMTP server in your email client to the appropriate server:
mail.optusnet.com.au
mail.bigpond.com

The second solution is to remove the port blocking. Only Optus allow you to do this. Please refer to the Optus link above.