Mac Mail - Outlook Exchange issues

DocEames My issue occurred before up grading to Big Sur, so it existed previously with Catalina. I honestly think I recall having this issue years ago, different employer and like 7 years ago but on the whole, I've not had issues where Mail never seemed like a poor alternative to the Outlook app. In my entirety, it's been probably 4 days total that I experienced the issue. Have you tried clearing the trash/junk maybe even old folders of saved mails and attachments? I found that the app CleanMyMac X has a feature to go through and remove the local copies of attachments to email, which in my business can be large files. The file still lives on the server so if I open an old saved email with an attachment that the local copy has been removed it automatically re-downloads the attachment. 

Not sure if i mentioned on this thread before, but my wife's company iMac she works on from home now, if she runs the Outlook app, after some point, or load on the computer, the screen will blink out, on off, white and black flashes and feels like a graphics card going bad. BUT shut down the Outlook app and problem goes away. She now uses Outlook in a web browser and I keep telling her I'll help her set up the Map app to do the Exchange account. HA

DocEames  Hi, I struggled with this for years ( still do for people I support but I use Outlook) and Apple has neglected the Mail App. My current issues magically went away after I escalated with MSFT and Apple. If only they would reveal the cause we could all jump to the band-aid solution immediately and have them implement it each time instead of the support desk being totally unaware each time. It doesn't permanently won't fix the issue but would expedite the resolution each time.  Outlook works because it uses a different protocol to retrieve email and if you flip the "New Outlook" switch, in outlook for MAC,  it looks very much like Apple Mail. (Sorry, I had to throw that out there. ) Then just use the native apple contacts and calendar because I find Apple Mail user don't like the fact that the calendar and contacts in Outlook are a tab at the bottom of Outlook for MAC and you can't pop out the separate Windows.  You do need to make changes/additions  from the Outlook Calendar and contacts tab or through or your phone; I've seen issue otherwise with updates.  So I recommend using the latest  Outlook and uncheck Mail in the Internet settings and just ( my experience not documented anywhere ) leave Contacts and Calendar. If you are stuck on Apple Mail make sure to keep you item counts down to less then ~20K for each folder, no subfolders if you can help it and the size  below 15GB.  You need to rebuild from scratch each time this happens. The one off rebuild brings down the new mail but will not continue work; you have to hit rebuild every minute which is not useful. I wish I knew the root cause and I know someone at MSFT or Apple engineering does but perhaps they blame each other? ( long history their)

DocEames 

Thanks. I updated for Big Sur 11.1 to Big Sur 11.2 and for the time being Mail seem to work fine with the Exchange account. Mail keep coming in without me having to restart Mail to receive new mails.

Guess Mail had an issue they fixed. Keeping my fingers crossed that it stays this way.