If you are upgrading the Outlook Add-Ins from a version earlier than Enterprise Vault 8.0, note that some Vault Cache advanced settings and Outlook Add-Ins registry values have been removed from Enterprise Vault 9.0.
These advanced settings and registry values were present in Enterprise Vault 8.0, including service packs, but they only applied to Outlook Add-In versions earlier than Enterprise Vault 8.0.
The Vault Cache advanced settings that have been removed are as follows:
The Outlook Add-Ins registry values that have been removed are as follows: