Sometimes you receive a mail bounce report i.e. 503 Valid RCPT command must precede DATA while sending mails from Microsoft Outlook.
Your message did not reach some or all of the intended recipients.
Subject: mail subject
Sent: (Date and time)
The following recipient(s) cannot be reached:
‘Ashok Koli’ on (Date and time)
503 Valid RCPT command must precede DATA
This error indicates- the server is not able to accept the message because SMTP connection is not authenticated. By default, SMTP authentication is enabled at the servers.
In order to avoid the error ‘503 Valid RCPT command must precede DATA‘, we have to enable SMTP authentication for the email account in Outlook. It means that before sending email, we must set up authentication.
Configure email client (MS Outlook) to authenticate automatically
- Open Outlook. Go to Tools >> Email Accounts, double-click on email account and click on More Settings.
- Open Outgoing Server Tab.
- Check “My Outgoing Mail Server (SMTP) requires authentication”
- Select “Use same settings as incoming mail server”
- Click OK and then Test Account Settings.
After authentication setup, the mails will be sent/delivered properly.
Sometimes this 503 error occurs when you have a corrupt outlook PST file. Try repairing the file. If you are still facing difficulties while sending the email, Kindly contact your Hosting support team.