selenium webdriver – Testing mail verification in organization domain

Requirement:

Users should sign up for an application using mail id and an email will be triggered to that mail account. Mail will have the verification link , once the user verifies he can onboard into the app

Email restriction:

Should be of Organization domain ( gmail / outlook / 3rd party mailboxes cannot be used)

Current manual flow:

We are creating org mail accounts, using temp mail providers and using that to sign up.

Question:

What is the best way to automate this requirement? Please suggest tools, APIs and other relevant inputs