What is Error 503 – Valid RCPT command must precede DATA

Error 503: Valid RCPT command must precede DATA happens when sending email. It’s telling you that your SMTP (outgoing mail) connection was not properly authenticated by your email server.

The two most common causes of this error are:

  • Your email server requires you to check email first before sending email. (Checking email first is one way your email provider manages the security of your email account.)
  • Your email client isn’t set up for SMTP Authentication.

Checking email before sending

When you first open your email client, it automatically checks email first. However, if you attempt to send email¬†after about 30 minutes and you see this message, simply check your email for new messages. You’ll then be able to send email if this is the problem (most common with Outlook).

More often, Error 503 tells you that you need to set up SMTP Authentication in your email client.

Setting up SMTP Authentication

Configuring SMTP Authentication in your email client requires you to edit your email account SMTP (outgoing mail) settings. Add your email address and password to the SMTP settings and you’ll receive no more Error 503 messages.

How you set up SMTP Authentication depends on the email client you use. Here’s how to set it up in Thunderbird version 52:

  1. Open the Tools menu and select Account Options.Thunderbird SMTP Authentication
  2. Scroll to the bottom of the Accounts panel and click Outgoing Server.Thunderbird SMTP Authentication
  3. The Outgoing Server (SMTP) Settings display in the right panel. Select the SMTP server you wish to change and click the Edit button.
  4. The SMTP window opens.Thunderbird SMTP Authentication
  5. In the SMTP window, set Connection security to SSL/TLS, Authentication method to Normal password, and enter your email address in the User Name field. Click OK to save your settings.

The first time you check email you’ll be asked for your account password. Enter your password and click the Save Password box to save your password and avoid having to re-enter it in the future.

If you continue to receive the Error 503 message, please open a support ticket from your HostPapa Dashboard. Follow this link to learn how.

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