Hi @davetqm,
Outlook 365 connector is an integrated service in microsoft flow,if you have a subscription of microsoft flow,you will able to use the connector.
Do you want to create a outlook flow and don't want to sign up for flow trial?
As is mentioned in the flow pricing:
https://preview.flow.microsoft.com/en-us/pricing/
Office 365 Enterprise E3 plans includes Microsoft Flow,if you have a office 365 E3 tenant as you mentioned, you could sign in microsoft flow with your office 365 account without sign up for flow trial.
Best regards,
Alice