This article covers methods to fix the email error, "503 bad sequence of commands" which happens as a result of a number of reasons.
To resolve SMTP response: 503 Bad sequence of commands, consider the following and also read the complete guide here.
The IP that should be 10.0.0.0 - whatever that is, look at that box, this is where the problem is likely to be.
Your internal domain is domain.com or domain.net etc.
You may also add a test email account and check if it works as expected. If this works, then this could be an issue with the email account or with the service provider.