Error 503: Valid RCPT command must precede DATA

This error (Error 503: Valid RCPT command must precede DATA) usually refers to email being sent without authentication. Most email servers do not allow mail to be delivered if the mail was not signed by authentication.

To clear this error, you should enable outbound email authentication on your email client (E.g Outlook). The below steps covers enabling this on Outlook however this can be done on all email clients.

1. Firstly open Outlook.

2. Click on File → Account Settings

3. Select the account in the list you would like to change the settings for and click on ‘Change’

4. Once open, click on 'More Settings'

5. Navigate to the Tab 'Outgoing Server'

6. Select the option 'My outgoing server (SMTP) requires authentication'

7. Select the option 'Use same settings as my incoming mail server'

8. Click on Ok.

9. Click on 'Next Step' to complete updating of the email settings.

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