Increase Message Store Capacity Outlook

If you get an .OST of 50 GB + then Outlook will start crashing, and you need to edit the registry to allow for mailbox max size of 75 GB or 100 GB.

You will also need to set warning size of 95 % of 75 GB or 100 GB, whichever you choose.

The steps are outlined here:

https://www.wintips.org/increase-maximize-outlook-2003-2007-2010-2013-pst-file-size-limit/

Proceed with caution, and export the Registry prior to making changes, then restart the PC.

These solutions can cause instability meaning you have to rebuild the Outlook profile.

If you rebuild, but still get Outlook is copying information to new email on Outlook startup issues, then you will need to delete these 2 keys:

1. In regedit, go to: Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\PST

2. Delete the following two keys: LastCorruptStore and PromptRepair

3. Start Outlook

Best practices:

Backup Outlook address books and Contact Groups.

Export OST to PST

Copy signatures and Stream Autocompletes to new profiles etc.