503 valid RCPT Command Must Precede DATA Outlook 2007

[thanasis]

Hello all,
i have problem with all clients using Outlook 2007, they can't send email...
I have returning emails with error "503 valid RCPT Command Must Precede DATA"
This is not happend at Thurdirbird...
At outlook settings i have got "Log on to incoming mail server before sending mail".
I have at SMTP port 25...

 

[Infopro]

Check this thread to see if it's of any use to you:
SOLVED - Unable to send emails properly