If i switch to libre office what do i replace outlook 2016 with?

I do not see a replacement for outlook 2016 am I missing it?

Please browse through Q&A’s tagged with “outlook” for previous discussions of this frequently asked question.

Note also the recent(ish) news about the possibility of LibreOffice and Thunderbird, with further evidence in the Document Foundation wiki. Probably worth having a look at Thunderbird, then.

Yep. No effective (feature comparable), drop-in replacement. Main Q/A is this one.