For a very long time, it was thought gospel that Outlook had hard caps on size of PST and OST files, which equals a hard cap on the size of a mailbox that Outlook can see. This has, apparently, changed. 100-gigabyte OSTs are possible, and larger. It is thought that very fast hard drives primarily, and certainly also good CPU and lots of RAM, are needed to reliably handle huge mailboxes and PSTs without corruption. Here is a method by registry entries. It’s also possible by Group Policy.
Today it was found that an Office 2019 installation via 365, did not have any of the registry keys involved. After creating them manually in Regedit, the desired results did occur. These very registry entries are also created by the Group Policy method.
Once you install the Office 2016 templates:
you can set the maximum sizes:
This creates the same registry entries as the manual method.
As of version 2019 (and possibly before), QuickBooks has a new feature: native support of Office 365 webmail and some other major email providers. When users send email via QuickBooks, go to Preferences, Send Forms, and instead of choosing Outlook, choose Webmail, and then set up integration with the user’s Exchange Online account. Works much smoother, faster, more reliably.
Sometimes, newer versions of Outlook will hard-fail a plugin, so that none of the standard GUI changes will permit it to reenable. When this happens, you can override by deleting everything here:
This does enable every plugin, so there is a bit of danger.
At long last, as found by the astonishing Tharin Brown, we are given an Outlook repair tool that really works!!!:
Outlook has many command line options. Several of them do various forms of cleanup, and this can help Outlook performance a lot. To do them all (as of Outlook 2013 and 2016):
C:\CLEANOUTLOOK.CMD containing the below:
- Find a working Outlook shortcut, do a Shift-Rightclick on it, and choose “Open file location”
- Copy that path (e.g.,
C:\Program Files\Microsoft Office\root\Office16), paste it into a non-administrative CMD after CD, to get the CMD into that folder