We been troubleshooting this for many years, and it's becoming so ridiculous at this point. Some reason this user was delete from the AD many years ago. This user was given a permission on the CEO mailbox calendar. Every time someone send the CEO a meeting invites, this error below bounce back to the sender. But the CEO is getting the invite, it's just becoming very annoying at this point. PLEASE HELP!
Diagnostic information for administrators:
Generating server: xxx.domain.local
#550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ##