Hello @Emmanuel Arroyo · Thank you for reaching out.
When you add a domain to Azure AD, it gets added as unverified domain. In order to verify the domain, you can create a TXT record in your Domain and verify the domain afterwards. Once the domain is verified you can create users with Email address suffix of your domain e.g. username@your_verified_domain.com by assigning a mailbox.
However, to send and receive emails, you would need to create MX records pointing to O365 mail servers. You cannot have MX records for both Google and MS at the same time.
In short, you can add domain in Azure without disrupting your existing email but to send/receive emails from the new provider, existing provider needs to be stopped.
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