Duplicate Sent Items Even thought the box is checked to not save

[CBuongio]

Fairly recently my Outlook 2016 (through Office 365) has started duplicating all of my sent items.  I use a Gmail account and have followed the steps as instructed for outlook, as in the box has already been checked to not save sent items - but it doesn't matter, still does.  I am using Windows 7 Professional, which I understand is no longer supported - does this impact the operation? Any suggestions would be helpful.

Thank you

[#2]

@CBuongio The OS shouldn't have an effect.

When you checked the setting in account settings, did you untick 'Don't save copies of sent items', save and exit the dialog then go back in and re-enable it?  If that doesn't fix it,  turn off the option to 'Save copies of messages in the Sent Items folder' in File > Options > Mail, do you still get duplicates?

[#3]

@Diane Poremsky 

Thank you for the reply, I ended up doing an On-line repair to the Office 365 and that seems to have corrected it, I had previously tried the quick repair with no luck.  Hopefully it will not start up again, if it does I will try your suggestion.

[#4]

@CBuongio I have the same issue, mine was already unticked from resolving the issue previously, but it's come back today, are you able to provide the link for the repair tool?

[#5]

@ilonka65  it's on the help menu in outlook or can be downloaded here - https://aka.ms/SaRA-OutlookAdvDiagnostics 

More info on it here - 

Scan by using Microsoft Support and Recovery Assistant - Outlook | Microsoft Docs

[#6]

@ilonka65  oops - that was for SaRA - the office repair option is accessed in Windows Settings. 

To repair your Office installation, right click on the start menu and choose Apps & Features, find and select the Office installation. Choose Modify then select the desired repair option.  In this case, try the online repair option.