Site can only send from admin email address

We have the “WordPress Notification Email” set to something like [email protected]. Up until recently, it was possible to have Gravity Forms send notifications from any email handle as long as the “From Email” email domain matched what was set in the “WordPress Notification Email” field. For example, notifications would be delivered successfully by setting the Gravity Forms “From Email” field to [email protected] or [email protected].

Since upgrading to WP 5.6 in mid-January, this is no longer the case. Notifications will only send if the “From Email” field exactly matches the “WordPress Notification Email” set in the Offload SES settings (i.e. [email protected]).

Any ideas why this might be the case?