Hi Happymum,
What's the type of the email account configured in Outlook for Mac?
How about readding the account to see if there will be any improvement?
Office for Mac has released 16.10 recently, please try checking for any install the
new updates and check if the issue can be fixed.
Generally, slow performance issue can be caused by various reasons. If the problem still persists, please refer to the following article for more possible resolutions:
Outlook is running slowly
Hope this can be helpful.
Best regards,
Yuki Sun
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