Why do I keep getting an email saying Action needed on your email channel?

That email is sent when a connected email domain or channel needs attention, for example a domain added in the SaaS Configurator whose records are not passing the check.

If it is a domain you do not need, for instance a subdomain you do not want to send email from (most people send email from the root domain), remove it in the SaaS Configurator and the emails will stop.