How do you handle email support if you host your clients website?

I am thinking of hosting clients' websites as a service however I don't want to be bothered with having to handle support for business email problems that may arise. Any solutions for this?

I am thinking of maybe having them use a service like Zoho for emails but then not sure how to justify them that you are using another service for their email.

Also anyone has any experience with using duda for a web design platform for clients? If so how did you handle client business emails?

there are many smtp providers like mailchannels that can do the job for you,
you just need to setup the smtp authentication via whm/cPanel and you are good to go.
If you are not using whm/cPanel still you can use third party smtp gateways for emails