Ok so as background:
IM "the IT" for small/medium sized horeca company (200PC full time users 1000 non office workers total AND 3 person IT team)
i only have few years of experience in being anything more than T1 helpdesk explaining advangages of restarting PC

So without further ado....

Cheap Hosting of Emails with servers inside EU, pref Poland?
I currently m hitting 6th TB of Emails
since i cannot find anything higher than 1tb and most offer 300gb max i m
i m currently hitting 9th? diffrent host for mails used at once

becouse of nautre of buisness we own like... 200? diffrent domains that are used

with amount of internal and utility mails Microsoft Outlook and Google offers with per user payment make no finantial sense to choose them

I have decisionmaking power to transfer us or can get budget for investment
and m thinking about better email solution than basing it off multiple vendors
couse only alternative is paying per user to MS or Google and it would bring monlthy cost by unresonable amount

TLDR:
Please point new guard towards right email solution