I have a customer with Zimbra mail server (on premise installation).
Does Sophos Email support this server?
They want to review outbound email traffic.
Thank you for contacting the Sophos Community.
No natively like Gsuite or O365, but you can select the Custom Gateway option.
If you need assistance with the configuration or want to know if specific features that Zimbra uses will work with Central Email, please reach out to your Sales Engineer for a PoC.