My company (Company B) has been acquired (Company A), and the Company A CEO wants Company B employees to immediately be able have a Company A email address. So firstname.lastname@example.org. Due to SSO and other compliance issues, we cannot change our Company B domain yet.
How do I add the ability for Company B employees to send with a company A address, yet still be able to receive email from the old domain and new domain? Both company's employees need to see each other in address books and I think I can accomplish that with contacts.