Steps to fix “503 Valid RCPT command must precede DATA”
- In Outlook, click File
- Click Account Settings > Account Settings
- Select your email account.
- Click Change
- Click More Setting
- Select the Outgoing Server tab
- Check My outgoing server (SMTP) requires authentication
- Select the Advanced tab
- Change Outgoing server (SMTP) to 465
- Set Use the following type of encrypted connection to SSL
- Click OK
- Click Next