Can anyone help with 503 valid RCPT command must precede DATA in Outlook/Vista?

[#1]

When trying to configure outlook (Vista/OneCare) I can't send e-mails. I get error message
server returned: 503 valid RCPT command must precede DATA.
I'm a PlusNet customer.
Can anyone help? Thanks
Gill

[#2]

Just a quick one off the top of my head. Are you using your email address in the correct format, mailbox@username.plus.com?
After a quick google, it might be worth receiving any emails waiting before trying to send out.

[#3]

Are you trying to send via the Plusnet relay servers (relay.plus.net) ?
AFAIK, this is related to "check before send" relaying, which I didn't think PN implemented.
Basically, there should be an option within Vista Mail to "check for messages before sending messages"
[quote=random website somewhere]
Pop before smtp - check your email account for new mail before trying to send email. This adds your IP address to a relay hosts file and allows any email to be sent from your IP address for up to 30 minutes. After 30 minutes you have to authenticate again. You may also have to authenticate again if you are disconnected from your dial-up connection.
If you are using Outlook then under Email Accounts within the 'more settings' for SMTP you can select always check email first.
That applies to Outlook - I'm assuming Vista will have a similar setting.
If you *are* trying to send via relay.plus.net, then I would suggest removing authentication on the outgoing mail server - this may be causing the problem.
B.

[#4]

Barry googled the same site as me

[#5]

This error is often generated by a malformed (i.e. invalid formatted) from email address. So check you have set your correct email address.