Cloudron will work in this case?
I create blogs on Wordpress for clients. I often get a request for an e-mail service and a subscription service (newsletter) which I do not offer. I thought about Cloudron, to start offering these services with Mailtrain and Roundcube applications. One installed app for one client.
Is it a good idea? Will Cloudron work in this case?
Yes that should work fine. Based on the information you gave, I assume each one of your customer has an individual domain, which can be added to your Cloudron and then the corresponding apps installed on subdomains of that. Once a domain is added, the email server and mailboxes can be managed for each domain individually.