Outlook Mobile proxy through ms servers. A way to stop that?

[12345678]

I can't change client, I can't find a fork or anything similar without ms proxies

 

The problem is that there's a firewall in place, adding this range of ips:

https://learn.microsoft.com/en-us/microsoft-365/enterprise/urls-and-ip-address-ranges?view=o365-worldwide

Does not seem to solve

 

The mail server used is an old exchange. I can't find anything specific to it, but online the ip/urls are supposed to be the same as 365

 

Any other random mail client works, but the management is... Whatever it is, and refuses to use anything else