Try this extension for Google Chrome - it removes the space on the right:
Webmail Ad Blocker
Webmail Ad Blocker - Chrome Web Store
What I did was to remove the
uBlock Origin extension, then install the
Webmail Ad Blocker.
Refresh Outlook.com and check that the adds had gone and the space on the right was ‘reclaimed’ (it works).
I then reinstalled
uBlock Origin (optional) as I rate this blocker highly.
Re EM Client – my main email client is Outlook 2016 and have EM Client as a back up.
In my opinion, it is one of the better free email clients available – give it a try.