Not sure if there's a mail server for the V4 cloud yet
According to the docs:
https://docs.mendix.com/howtogeneral/mendixcloud/migrating-to-v4
What are the limitations?
Initially, we won’t have a mail server. You can use a third-party email provider instead. VPN, which is already deprecated in favor of client certificates, will not be possible in the Mendix Cloud v4. See the Certificates documentation for more details.