The error 503 Valid RCPT command must precede DATA essentially means that the server was unable to accept the message, usually because the SMTP connection was not properly authenticated. Users who uses MS Outlook to retrieve ands send their email occationally experience the error when SMTP authetication is enabled. Please browse thru below to perform possible solutions for this error.
To fix this error in outlook
- From the Menu Bar, Click Tools then Click E-mail Accounts
- Select "View or change existing e-mail accounts" then Click "Next"
- Select the Email account and click "Change"
- Click "More settings"
- Select the "Outgoing Server" tab
- Select the box beside "My outgoing server (SMTP) requires authentication"
- Select "Use same settings as my incoming email server"
- Click OK, Next and then Finish.
NOTE : In Outlook 2010 and later, the Email account can be selected by going to Menu bar >> File >> Info tab >> Account Settings
Other possible solutions if the above changes did not work:
- Remove any special characters or symbos in your email address.
- Make sure you are not behind a corporate VPN or firewall, if so try connecting outside the VPN.
- Antivirus or filter in your PC/Mac might be interferring with the connection.
- SMTP port block by your ISP.
- Corrupted Outlook profile. If alll the above solutions are tried but nothing works, your Outlook profile might be corrupted. Try re adding the account to outlook or repairing the PST file using a microsoft recommended repair tool from their website.
For server or vps owners make sure that SMTP authentication is enabled in the WHM >> Tweak Settings
