If you receive the error "503 Valid RCPT command must precede DATA", it normally means that you need to turn on "My outgoing server (SMTP) requires authentication".

The error looks something like this:

Here are some directions for how to turn it on in Office 2007. (There are multiple ways to get to it, this is from inside the program)

1. From the Tools menu, select Options.

2. Click on the Mail Setup tab, and click on the Email Accounts button.

3. Double click the primary mail box or highlight it and click Change. In most cases there is only one listed.

4. Click on the More Settings button.

5. Click the box to put a Check beside the "My outgoing server (SMTP) requires authentication" and click OK.

5. Close all option windows and try sending your email again.

If you still have problems after this, drop me a line and I will see if I can assist further.