M365 apps for Business - Plan question re: Email Integration

[JForth]

I have a question regarding M365 Apps for Business. I'm setting up a tenant for a Doctor's office.  Their email is managed by a third party.  They have the Apps for Business license that's $8.25 / user carried over from the older O365 license scheme. 

Is there a way to link their account with their third party email hosting service to communicate with Teams, etc. without upgrading to the plan that has Exchange Online?  They'd like to be able to fully use Teams, but not by moving to the more expensive M365 plan. 

[#2]

No, for the full Teams experience, you'll need an Exchange server, or preferably an Exchange Online mailbox as detailed here: https://docs.microsoft.com/en-us/microsoftteams/exchange-teams-interact