Send from Outlook through your domain and route incoming mail into Axene.
Verify your domain and create an Axene SMTP credential.
In Outlook, add your domain address and set the outgoing server to mail.axene.io, port 587, STARTTLS, with your Axene credentials.
Add an Outlook rule that forwards incoming mail to an address on your verified domain.
A native Microsoft 365 connector with OAuth is on the roadmap.