Why did archiving my email in outlook 2016 not move everything I selected to the archive pst file.
When creating an archive.pst file in Outlook 2016 only part of what you have selected is copied to the archive file. The default for cached exchange mode in outlook 2016 is to keep 6 months of mail off line.
This must be changed to keep ALL mail off line (slider to the right)prior to the archive being created since the archive is built from the local cached email.
To change the setting close outlook - open windows control panel - double click Mail (32bit). Click the Email accounts button, double click your email address and check the "Use Cached Exchange Mode" box (if not already checked. Then move the slider fully to the right and it will say "All". Then click next, finish, close and close. Open outlook and wait several hours for the local mail cache to sync ALL of your mail. After that email archiving can be done.