I get an error when I send mail from Outlook, Outlook Express, Thunderbird etc

If you received an error message (553) while sending an email via Outlook, Outlook Express, Thunderbird or other PC/MAC based email software, your alternate eMail address is probably not verified.

This problem may affect you if you are using Sky or BT Yahoo! as your internet service provider.

This is a security requirement by your ISP. If you are trying to send email from myemail@mydomainname.co.uk via BT Yahoo or Sky, you need to tell them about your email address to allow you to use their email servers to send your email.

You must verify your NON-BT email address with your ISP in order to send emails via their email servers.

Please visit the yahoo forum for more information or contact your Internet Service provider and explain the problem to them.