I have configured the Office 365 settings for a new tenant. The mail domain "@thedomainname.de" is configured for Skype for Business and Teams (DNS).
But if the user create a teams meeting and add an external mail address, the invited person get no mail.
M365 Admin-Domains: no error
Exchange Admin Center: the user with the mail address (MX at other provider)
But Exchange online should not be used for MX records/mail flow.
Is there any way to get teams invite mail flow working without use Exchange online for the mailflow (MX, user mailboxes)? Actually the customer would like to use his old mailbox provider for all mails (excepted Teams outgoing meeting mails)
No they cannot. Teams requires exchange as a requirement. It actually uses the exchange mailbox of the user to send these messages via calendar / meetings or it will use the group mailbox for the Team if it’s a channel meeting to go out to team members.