true
as tcecyk already pointed out above there is no need to install DAVx5 because the accountmanager (which is integral part of /e/ system settings) actually is (a fork of) DAVx5 and that´s where you set up your caldav account. (of course you can do this little extra install or use opensync etc. but there´s really no need to do so from a technical/functional perspective)
@coustou Are You 100% positive your outlook is capable of CalDAV-sync in the first place?
I´d be surprised.
I presume that /e/ is not your problem, it´s rather outlook - to my best (but maybe aged) knowledge outlook does not provide a native interface to serve CalDAV synchronisation.
To achieve CalDAV-sync with outlook you probably still need some extension installed in your outlook-application (my experience is a few years old)… search for keywords like “outlook caldav sync” in your favourite search engine and find some options … if you have no admin privileges at your office-pc you may try to convince your admin to install it.
edit 1: this one worked pretty good for me years ago: https://caldavsynchronizer.org/ there may be others or better options, just an example
edit 2: from what I recall it worked for me only because I synced outlook (via extension) with an online-instance/cloud that hosted my caldav “master” and from there to my phone… I assume trying to sync outlook directly with your phone will not work … my way of explanation: outlook (incl. extension!) is able to sync with caldav but it does not provide/host caldav for sync (? 
) … the latter is what you need for sync with your phone.
I therefore guess you will need that “caldav-capable-cloud”, e.g. /e/ (murena) cloud in between … your chain of dependencies would then be like this:
outlook incl. extension (tbd) ↔ cloud (hosting caldav-calender, eg murena, nextcloud or else) ↔ your phone
… could be done