Hi Madalina,
Thanks for your reply.
I have tested my Office 365 account on Outlook for Mac 15.6 and it works well. To further narrow down the issue, could you please provide the following information:
1. Can you try your account on Outlook for Mac 15.6 under another network?
2. For “Yes, we're using the same account and client on 2 macs; both of them have the same issue”, do other people’s accounts works well on Mac? If yes, can you try your account on their good Mac?
3. Did you try deleting your account and re-adding it again?
4. When you mentioned “When configuring another exchange account on the 15.6, I didn't encounter the same problem.”, do you mean this exchange account is an Office 365 account under the same subscription?
5. Can you send a test email and please upload some screenshots of the inbox in OWA and Outlook for Mac 15.6? To protect your privacy, I have sent you a private message to collect this information. To read it, you can follow the steps below:
a) Go to the your details section on the right side of the community site.
b) Click Private messages.
c) Click the subject title of the response to read the message.
d) You can reply by using the form in this display. Click Submit Reply.
Best Regards,
Erick