Having the same issue.

I'm also hosting outside odoo server. Using the https protocol all around but request sent for mail connection to outlook is http. I think it's odoo's internal issue. The code responsible for sending the request is missing an 's' in the syntax.

Can someone suggest the code where this can be set?

Mera Code for the win.  Dropping the answer a few times in here to make sure it's listed right, or at least cataloged.

Mera Code  2 days ago

Found the culprit. It was a parameter put wrong.

Developer Mode -> Technical -> Parameters -> System Parameters -> web.base.url

The URL placed there didn't have https.

Hey Albert!

So, I am waiting to hear back from someone.  But let me go over my layout to see if we're both setup the same way

I am using a self hosted version, in docker.  I'm using cloudflared as my https.  I'm using the http://localhost:port  on my side, so, https is being presented over cloudflare, but locally as http.  

I'm wondering if that is the problem.

I have the same issue. Did you find a fix?