I have a user that has one person that was not receiving his email- no kickbacks no messages nothing. The receiving party's IT person told my user to fully type in the email address and it worked. The guys email address has a really long domain name so its a pain in the ass to re-type every time. Can't select from cached email address or even reply to an email from this guy without fully typing in the email address. I have never heard of this behavior in 20 plus years in IT.
There has to be a better fix for this.
Any ideas or knowledge of this situation?