Outlook 365 Freezing for up to 30 seconds when opening email

I am having an issue with the Exchange account of a person in our company.  She uses Outlook 365 to access her Exchange account on our email host.   When she attempts to open an email, Outlook will freeze for 5 to 30 seconds.  If she already has an email open and she attempts to use the previous or next item arrows, the email will freeze, and a small blue circle will appear for the duration of the freeze.  
 
 What happened:
 
 A little over two weeks ago this user's hard drive became corrupted.  I installed a new SSD into a spare PC of the same model and specs and configured Windows and patched it up.  I then installed all of the normal productivity software including Office 365 which we started using in January of 2020.  I configured her Outlook to work with our email host and installed the new PC that evening.  I received a phone call the next morning from her and she told me she was having the problems I described above.  And there my troubles began.
 
 What have I done to try and fix this:
 Please keep in mind I have tried many of these solutions multiple times across many PCs.  
 -created and recreated profiles about 20 times
 -disabled graphics acceleration
 -I usually run accounts in cached mode but I have tried both on her machines multiple times.
 -disabled all add-ins.  Tried add-ins one at a time.  It isn't add-ins.
 -safe mode.  Yes.
 -Contacted the host's technical support because I became convinced that the account had become corrupted.  The tech set her account up on a VM and connected to the account using Outlook in cached mode.  The tech was able to open and close email on the virtual machine without a problem.  He insisted that I use AnyDesk to login to the VM to witness that it wasn't the account.
 -After that, I configured her old PC with a new SSD.  I just installed Windows 10 and Office 365.  Same problems.
 -After a week and a half into this, I became convinced it was the account and decided to move all of her email out of the account to a PST and delete the account.  After I deleted and recreated the account, I sent 6 test emails from various accounts. I had the same problems with just those six in the account.
 -  This weekend I configured a PC with 32 Gigs of RAM and a M.2 SSD.  I installed Windows 10 from an MS installation disk rather than the Dell restoration disk.  I installed Office 365 and then configured Outlook.  Same problems.
 
 I have spent the last two weeks reading the same solutions over and over again.  If anyone has some insights, I am open for suggestions.  Thank you.