To pass DMARC standards, the From Sender and Return path on emails must have the same domain. The From Sender field in our orgs can be modified by users who are unaware of this best practice/policy, causing emails to go out with the mismatch and have a higher bounce/block rate. Either prevent another domain from being entered in the From Sender field, or provide a user friendly message/pop up that notifies the user that they have entered a mismatch - allowing them to make the correction before proceeding.