Outlook

to add an (external) mail account to Outlook on your Mac, you should start with these steps

your mail address

after selecting "Continue" Outlook tries to add an exchange account - to add a normal account, select "Not Exchange?"

deactivate "Sync with Microsoft Cloud" and select IMAP

enter the data of the server (to set up a mail account on an external server you have to add the socks proxy (macOS))

to add the mail account of your Uni ID give your mail address (UniID@...), as Username your Uni ID & the password of it, as incoming server imap.urz.uni-heidelberg.de with port 143 and the protocol "StartTLS" and as outgoing server mail.urz.uni-heidelberg.de with port 587 and protocol "StartTLS" (for other accounts it differs, e. g. for your KIP account the username is your KIP-account and the incoming and outgoing server is mail.kip.uni-heidelberg.de - with port 993 and the SSL-protocol for imap and port 587 and starttls-protocol for outgoing server)

your username instead of "xx000"

it's done