EMail address being rejected

I have a vendor who is attempting to send and email to me and it keeps getting rejected. We did some investigation and came down to the fact that the only strange thing about the email is it’s From address.

The vendor can send emails from all their other email addresses except this one. The difference is that this address has a single quote in the name (ie. O’Conner@xyz.com).

Does anyone have any ideas why this would cause the email to fail?

I’m running Exchance 5.5.