I regularly use seven browsers: Three different ones at work, two different ones on my home desktop and three different ones on my phone.

My webmail intentionally runs in it's own browser profile which is only used for opening links in email. If the tracking cookie attached there it wouldn't apply to nearly any of my usual web browser usage.

If you use Chrome for your browser, you can create a new profile and "web app" to run your web mail in. In Firefox, pin your web mail to a container. (Hopefully links followed from there stay in the container?)

On your phone, open links from email in chat in Firefox Focus unless you have reason to do otherwise. In settings disable third party cookies. (Firefox Focus still allows normal cookies by default)