Robertson misspelled my last name in an e-mail

Should he sent out a correction e-mail to everyone or is it one of those things no one really cares about?You would never send out a group e-mail to people and copy your source and spell there name wrong, but this setting is more personal so other rules apply. However, this is the 3rd semester in a row I've have with Robertson and you'd think he'd know it by now! :P