System Users or leftovers from AD/Exchange Takeover?

I’ve found some users in my system which are not listed as system users here:

SM_5c977e3075d840999 MSExchApproval
SM_6fa4a7d4e74d4fcfb MsExchDiscovery
SM_8cdc4c19f298483fb FederatedEmail.
SM_15dc6b554e5e4197b MsExchDiscoveryMailbox

The righthand names are followed by a string of letters and numbers.

Can I delete those users safely?
Or at least hide them as they are listed in nextcloud also which bloats the list.

Thank you very much!

The four you’ve listed are definitely not part of a default UCS installation. They all sound like remnants of an Exchange installation and can therefore be removed safely.