Office 365 (outlook) not saving sent emails on 1 account

I did post this in an Office 365 forum but without result. Maybe someone can help me here.

I have 3 emails that I use with Outlook 365. Somehow, I have messed with settings so that one (and only one) of the emails doesn't save sent emails.
The settings look the same to me, but I recall there was a special setting list that I changed and can't get back to.
Any help is appreciated.

Still looking for help.

• Outlook (365) is updated.
• My Hotmail account (also exchange) saves sent messages.
• settings have save messages checked.
• Web version of outlook shows the missing sent messages

Have you verified that the troublesome account is actually sending the emails in the first place. They may not really being sent. Thus they would not appear in your sent folder.
Try removing the account from Outlook 365. Restart, and add the account back.
What is the domain name of the faulty account? Setting up as imap or pop?

Yes, they are being sent and received and as I mentioned they show as sent in the web version of Outlook.
I've considered deleting the email account , but wouldn't that mean I would lose my email folders?
The domain is a private country club site, and just like Hotmail (that doesn't have this problem) it uses Exchange (MSE) not pop or imap.
I'm sure it's a setting somewhere that I messed up trying to stop OneDrive copying my PC desktop to my much smaller laptop, I just can't find it.

I checked and although the laptop only had the account created in the last 14 days (I had to get the admin to reset the password) it has the same problem of sent messages not being stored.

I'm game to delete the email from both devices but really don't want to lose the folders and their content. Other than copying the folders to my Hotmail account, deleting the problem email from both devices and then adding it back and copying the folders back is there a better way to save the folders and messages?

OK found EaseUS Todo for the backups

Follow Up, perhaps interesting to some.

My experience with EaseUS Todo was not great, didn't work for me and they kept offering more options to purchase SW to "solve my issues".
I contacted MS, that was a bad experience until I got to "chat" with Arnel. My problems with Outlook and OneDrive would never have been fixed by 3rd party SW.
The email issue is a limitation of how many exchange-based emails Outlook 365 personal can handle. Solved by setting up two MS accounts.
This allowed OD to be setup to save my working files to be able to be accessed by either PC without Icons copying over from desktops AND Outlook 365 now copies my emails between PC and laptop.

Thank you, MS, and especially Arnel.