Step 1: Open Outlook Email client.
Step 2: Select your IMAP account settings via File-> Account Settings-> Account Settings…-> double click on the IMAP account.
Step 3: Press the button: More Setting.
Step 4: Select the Sent Items tab.
Step 5: Click the Radio button Do not save copies of sent items and click OK button.
Step 6: Now you have disabled the sync IMAP sent items in Outlook.