This topic keeps getting resurrected because many folks are uninformed, younger users who have entered the world of computing and others are looking for some magic cure for various system problems. If you have been using such a program routinely or followed the advice of some so-called technician. There is no telling what damage it has already done to your registry and other areas it purports to clean.
I suspect that is the reason for your registry error messages unless it it is the program you are currently using which is giving the errors. There are numerous programs which purport to improve system performance, make repairs and tune up a computer. Many of them include such features as a registry cleaner, registry optimizer, disk optimizer, etc. These registry cleaners and optimizers claim to speed up your computer by finding and removing orphaned and corrupt registry entries that are responsible for slowing down system performance. There is no statistical evidence to back such claims. Advertisements to do so are a marketing ploy intended to goad users into using an unnecessary and potential dangerous product.
If you're using an Exchange email account, you can delete the offline Outlook Data File (.ost) and Outlook will recreate the offline Outlook Data File (.ost) the next time you open Outlook. Notes: The Inbox Repair tool doesn't connect or analyze any data stored in an Exchange mailbox.