This error message signifies that the email server rejected your message due to a mismatch between the "From" email address and the SMTP username (phpmailer, jenkins).

What Triggers This Error?

This issue commonly arises when using third-party plugins that send emails with their default email addresses, which often differ from the actual SMTP username.

Resolving the "SMTP Error: Data Not Accepted"

To fix this error, ensure that the "From" email address in your email message matches the username you're using for SMTP authentication (phpmailer, jenkins). While some default settings might not enforce this alignment, you can often configure the system to force the "From" address to match the SMTP username.