503 valid RCPT command must precede DATA

The server responded: 503 valid RCPT command must precede DATA

means you must check your email before trying to send mail. The mail server requires authentication, which can be achieved using one of these methods:

1. Pop before smtp -- check your email for new mail before trying to send email. This adds your IP address to a relayhosts file and allows any email to be sent from that IP address for up to 30 minutes. After 30 minutes you have to authenticate again.

2. Configure your email client to authenticate automatically by checking the "my server requires authentication" box in your email configuration. You will be able to send mail without having to "pop" your mail box first.

Outlook Configeration

Outlook Configeration
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1. In Outlook, go to the Tools menu and click on Email Accounts.
2. Select Add a new email account and then click Next.
3. Select POP3 and then click Next.
4. Enter your email information:

Your Name: your name
Email Address: matt@castleman.net (the email address the messages will be sent from)
Incoming Mail server (POP3): mail.test.com
Outgoing Mail server (SMTP): mail.test.com
User Name: matt@test.com
Password: the password for the email address

5. Click on More Settings and Select the Outgoing Server Tab. Check My outgoing server (SMTP) requires authentication. Select Use same settings as my incoming mail server.

6.Click Ok. Click Next. Click Finish.

If you cannot send email using mail.yourdomainname.com as your SMTP server,
it may be because your ISP is blocking port 25 on their network, used for sending outoing mail via the SMTP protocol. In this instance, we recommend using your ISPs outgoing mail server, which can be obtained from your ISP.