Should I use subdomains for email, and how does their reputation work?

Yes, using subdomains for different mail streams is a widely recommended best practice. It allows you to isolate reputation so that problems in one category do not contaminate others.

A typical setup might include mail.tidalmail.com for transactional receipts, news.tidalmail.com for marketing newsletters, and support.tidalmail.com for customer service. Each subdomain develops its own independent reputation based on its specific sending behavior and recipient engagement.

New subdomains may initially inherit some trust from the parent domain, but they quickly establish their own track record. This inheritance works both ways. A subdomain with terrible reputation can eventually drag down the parent if providers detect patterns of abuse.

Subdomains are like separate vessels in your fleet. Each sails under its own record, protecting the others if one runs into trouble with the harbor authorities.