According to the documentation you need to call

/users/{id | userPrincipalName}/sendMail

I could not find it in the module, however it is stated in the documentation

Typical usage scenario

• Allow users to use their Outlook mail to send and receive emails

Best option for receiving mail is to subscribe to 'message'

https://learn.microsoft.com/en-us/graph/api/subscription-post-subscriptions?view=graph-rest-1.0&tabs=http