I have a single user who, every few months, has all internal emails sent to him kicked back with Recipient Not Found errors.
Address format is <firstname><lastname>@<domain>.com.
The x500 address Exchange is unable to find is ending with cn=Recipients_cn=<firstname>+20<lastname>@<domain>.com. I understand the +20 is a space, but I can't figure out why it wants to insert that.
Removing the user from autofill in Outlook & sending an email to him by either typing in his address or adding him from the address book resolves the issue for a few more weeks/months. I have multiple users complain about sending email to this person, but no other users seem to have their email kicked back like this one.