Exchange Server CAL licenses - which is better CAL, DEV or USR or both?

Question

Licenses for software and other works

Hello!
I'm going to migrate from the old Exchange to the latest one, 2019
, I have a question about licensing, let's say I have 100 workplaces + half of the employees have access to corporate mail from personal devices,

what is the best way to license client licenses?
take, for example, 150 licenses for DEVICE CAL (cheaper) and thereby cover 100 PCs + 50 smartphones?
or take 50 DEV CAL +50 USER CAL (more expensive, by 1k rubles approximately)
and is it possible to license such a scheme?

DEV CAL applies to the device, while USR CAL applies to the user and all his devices.

Answer 1

Microsoft explains very well here that if several people access the server from one device (desktop), then you can take the DEVICE CAL.
If you have 100 PCs, and 50 of them use smartphones, then you only need 50 DEV CAL + 50 USER CAL.
Taking into account the fact that those who have DEV CAL do not access the server from another computer / smartphone.
There is one caveat, I really don't know how applicable it is in your situation. This applies to people "who used to work for the Company":
Q: Is there an External Connector license for Exchange Server 2019 for companies that want to offer email to non-employees such as corporate alumni or retirees (that is, “external users”) ?
A: no. External users do not require CALs to access Exchange Server 2019; access rights to standard Exchange functionality by external users is included with the Exchange Server 2019 license itself.
As far as I understand, these are those who are accessed from the outside via OWA, because as soon as they run a full-fledged client, the license agreement is violated.