No error message occurs.
The Enterprise Vault upgrade installer removes and reinstalls the Enterprise Vault SMTP Service as part of its installation routine. The reinstalled service is created using the default account, which is Local System for this service.
Reconfigure the custom logon account for the Enterprise Vault SMTP Service after the upgrade has completed.
Enterprise Vault upgrade packages from version 12.4.1 forward should no longer exhibit this behavior.
Note: Customizing the logon account for the Enterprise Vault SMTP Service is optional. It is not needed for the proper operation of Enterprise Vault.