We are enterprise organization and consider email as mission critical service.
We have around 1600 globally dispersed users in different countries and due to compliance issue we have to maintain backup.
Right now we have 3 geographically dispersed data centers and used real time replication for emails to achieve HA.
For last few months we are considering to move our email services to Microsoft 365 or googlemail to minimize OPEX without compromising service quality but like to improve our end user service.
I would like you guys to suggest on above case considering all above perimeters.