Some Useful Tips to Speed Up Microsoft Outlook 2016 Performance
It would be a good idea to delete your emails or find a way to split PST files to reduce the lag. Apart from loading, it also increases the time taken for reading, moving, and deleting email messages. Outlook stores all the data in the PST file, if the file size is enormous, then it could slow down the loading process. Why does Outlook Office 365 take so long to load? When the Outlook program suffers from performance issues, it can be caused by several issues.
Why does Outlook Office 365 take so long to load?.You can check how much time delay happens with each add-in and disable the add-in if you don't need it. This section will list out all the add-ins that causing slow performance and crashing Outlook. Scroll down on the right pane and click on the 'Manage COM Add-ins' button.