Things to check when you are encoutering problems when sending an email:
- First make sure you are using the correct server settings.
- If the error you saw is "553 sorry, that domain isn't allowed to be relayed thru this MTA (#5.7.1)" it means you should try to check for your email first, before sending one. This is called POP Before SMTP authentication. Microsoft Outlook has the option to do this under SMTP Authentication. Outlook Express just needs to check email first. Alternatively you can enable SMTP Authentication and enter your email address and password in the SMTP settings.
- ISPs often block outgoing port 25 to stop spam outbreaks. If you are using port 25 for SMTP (non ssl), try changing this to port 587. You can find this in the SMTP / Outgoing Email Settings of your email program.
- Alternatively try using SSL for SMTP which will use port 465.
- On a very rare occasion, rebooting Windows might help fix the problem.
How to set your email client to send emails through port 587
In Outlook Express, click Tools -> Accounts then select the account, click Properties. Click Advanced tab and change the SMTP port from 25 to 587.