503 valid rcpt command must precede data outlook error?

The solution to 503 problem:1. Uncheck the 'Tools->Account Setting->More settings->Advanced' page's Delivery 'Leave a copy of...' so that the server space is freed once you download a mail successfully.2. No single quotes in the names of the recipients (MS never thought of that for that matter)3.(This is what worked for me) Go to 'Tools->Account Setting->More settings->Advanced' and change the outgoing server to 'Auto' and again change 'Tools->Account Setting->More settings->Outgoing server' and check on the 'My outgoing server uses the same authentication as my incoming server' on.

If you have set not to remember passwords, even while sending the password will be prompted for but you will not get the 503 error.