I am not 100% sure, but I think you don't really need an account. I've had interviews where I got a link to a call/invite and opened it in the web browser. There was no need to sign in. Just enter a name and grant permissions for accessing cam and mic.

Same as in Zoom, actually.

Like someone else mentioned: you should be able to join meetings without an account.

That said, making an account with a custom email address will not create a microsoft mail inbox for you. Microsoft, however, will use your email address to send service-related messages. If I recall correctly, you can manage what kind of messages you want to receive, in your account settings.

The main difference is that you’d just be making a regular(free) microsoft account bound to an existing email address of your choice, as opposed to binding your domain name to a microsoft account to host your email there - which is mostly something companies do and is a paid service last time I checked.

Why not use an e-mail relay service like Addy.io or SimpleLogin.io? Much better than creating new e-mail accounts all the time.

But to answer your question. E-mails only get sent to wherever the MX records points to, so if your custom domain points to some e-mail service that is not Microsoft, Microsoft would never be able to intercept your e-mails.

I just setup a new Windows 10 VM this morning and it was the first time I was not able to skip making a Microsoft account. So I just used an email alias and then instantly paused the email address after receiving the verification code. Regarding your uncertainty around what seems to be Microsoft having access to the email inbox somehow, I can't see how that'd be possible unless the email is maintained by them or you decided to use Outlook. Use a burner email and make sure it's only provided for the Teams account and you'll be in a much better place than most Teams users.