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Resolve ‘503 Valid RCPT Command Must Precede DATA’ Error in outlook

Outlook Users who access their Email Accounts that are hosted on Servers faces an error "Error 503 Valid RCPT Command Must Precede DATA" while trying to send emails. This error generally occurs for those servers in which have enabled SMTP Authentication. The meaning of this error is that the server can't accept the email due to wrong SMTP connection authentication. In WHM Servers, one can do the authentication by SMTP or POP-before-SMTP Authentication. If the mail sender has not configured the Outlook properly for outgoing email like SMTP and also not connected with POP server just before sending email then you will face such kind of issues.

How To Solve This Error ?

One should enable the SMTP authentication in cPanel/WHM servers for the email account to resolve this error. Step by Step process for SMTP authentication in outlook is given below :-

1. Click on Tools and then Click on E-mail Accounts in the Menu Bar (In Outlook 2010 or Newer, Select Email Account by going to Menu Bar then File then Info Tab and then Account Settings).

2. Choose "View or change existing e-mail accounts" and then Click on "Next".

3. Now choose the particular Email account and then click on “Change”.

4. Click on "More settings" and choose the "Outgoing Server" tab.

5. Here choose the box “outgoing server (SMTP) requires authentication”.

6. Choose the "Use same settings as my incoming email server"

7. Finally Click on OK then Click on Next and then Click on Finish.

If the server doesn't allow SMTP Authentication then you should ask the customer to POP their email before trying to send them.

Apart from SMTP Authentication, there are some more causes of this error, the causes as well as their solutions are detailed in the text ahead.

1. Corrupted Outlook Profile –: Corrupt Outlook Profile is also a cause of this error, Re-adding the account into Outlook or repairing the Outlook PST file using “Microsoft PST repair tool” can resolve this.

2. Email Filter in the Computer –: If the user has installed any new Email Filter (Firewall) or has updated security rules then this error may occur.

3. Check for SMTP Port is not Blocked in ISP –: If the user uses port 25 to connect with the server and the connection is blocked by ISP port 25 then this error may occur. The user should use the alternate Exim Port 26.

4. Symbols in Username –: If username has any non-alphanumeric symbol in it then this error may occur and the symbols should get removed.

5. User Behind a Corporate VPN –: Some VPN Configurations can also cause this error so ask the user to connect without the VPN.
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Bhawani Singh
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