Tracking domain and deliverability


I'm here with similar and maybe kinda connected question with this topic.

1) We need to solve that the customer does not send emails on behalf of our app's domain - for example, the default tracking domain. We require and strictly control the quality of the email database, but sometimes poor quality contacts are found in the lists of our customers and this affects the reputation of our domain.

2) If a user has a verified tracking domain and uses it in campaigns, in emails outside of campaigns (e.g. double opt-in...) the tracking domain will not be used and therefore all links will still come from our app's domain. This means that if someone sends to low quality email addresses, it will negatively affect our domain - for example, we will be blacklisted. The deliverability of "list emails" such as double opt-in could be worse for other customers who use a tracking domain and quality database?

The deliverability and reputation of the domain is very important to us, so we are trying to figure out a solution, if you have any other ideas or could provide us some custom coding, we would be grateful.