503 Valid RCPT command must precede DATA

503 Valid RCPT command must precede DATA

You will get that error message if your mail client is not properly configured. To be exact, you missed to enable the option “My SMTP server requires authentication”. Once you enable it you will not see the error anymore. Check our guide how to configure your email address properly by visiting https://www.scalahosting.com/kb/configure-email-microsoft-outlook

Your firewall/antivirus system may cause that error to appear as well. If the error persists after enabling SMTP authentication in your mail client, try disabling your firewall/antivirus.

Why SMTP authentication is required?

If ScalaHosting mail servers do not require authentication spammers will be able to use them to send SPAM. Only authorized users can access the mail server to send messages. We do not allow any kind of open relays. In that way we keep our mail server IP’s clean and with good reputation.

Useful tip: ScalaHosting recommends connecting to all mail services via SSL. In that way you increase the security of the communication between your mail client and the server. All data is encrypted and noone can steal it.


Working in the web hosting industry for over 13 years, Rado has inevitably got some insight into the industry. A digital marketer by education, Rado is always putting himself in the client's shoes, trying to see what's best for THEM first. A man of the fine detail, you can often find him spending 10+ minutes wondering over a missing comma or slightly skewed design.

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