New Gmail/Yahoo Email requirements

Good Afternoon! After authenticating the new CNAME and DMARC records for the new policies introduced by GMail and Yahoo, I have an issue where email blasts are now being replied to and being received by the account email address on file within Constant Contact instead of the sending email address. Before these changes were implemented, the sending email address was arriving to contacts from  but now, they are arriving from. I cannot locate where to change this sending email address for email blasts. May I have assistance with this issue?