markets.books.microsoft

It IS safe to do so! I ran a scan with Bitdefender after allowing the exception, and no malware was found. Lots of certificates from legitimate websites and links are not updated sometimes. You just  have to research a bit. Microsoft uses that certificate, but apparently haven't updated it. It's used for their apps and programs. I found a Microsoft webpage that explained what that certificate was used for. Only when I allowed that certificate the exception, did my emails in Outlook 365 started coming in. I was frustrated for a week trying to figure out why my emails weren't coming in through 365! That's exactly when the certificate error started showing!. I tried EVERY process I could find to fix Outlook! Apparently, Outlook 365 uses that certificate. 

Outlook runs fantastically now, and there's no ill effects on my system. It's your call.

je ne comprends pas que Microsoft ne mette pas à jour ses certificats ?

It happens with the best of companies. I've seen many certificates from Google that aren't updated.

je vous remercie, pour votre réponse, mais il me semble, que Microsoft, pourrait faire un effort, pour mettre à jour

ses certificats, inadmissible.

Cordialement

The problem here is that the certificate is being blocked, and not allowed to be used because of antivirus software. Allow the certificate through the antivirus software.