This error could mean that you have the senders domain in your hosting/reseller account and hence its failing the spoofing check.
If the customer is sending from an external mail server and mail service is not hosted on our servers ensure the mail service for the domain is disabled within Plesk or cPanel.
Most Popular Articles
503 valid RCPT command must precede DATA
When sending email, you receive an immediate bounce such as the following:Subject: RE: XXXXXX -...
Domain example.com has exceeded the max defers and failures per hour (5/5 (100%)) allowed
Are you getting this error returned when sending email? Chances are one of your email accounts...
Why did I get an email warning about outgoing emails sent yesterday?
You may receive an email warning that a number of emails were sent from your account yesterday....
When I send out emails they land in the spam or junk folder on the receiver's side?
This could mean that: 1. The email being sent is too short or looks like spam.2. SPF and DKIM...
Why Is My Email Account Blocked and How Do I Unblock It?
An email account is usually blocked for one of two reasons: too many failed login attempts...
