I believe this to be a bug:

Add a contact and misspell the domain name.  Save the
contact and send an email (bounce back happens)

Edit the contact to correct the spelling of the domain
and save.

Again send an email to that contact.  The email will
continue to go to the original email address.

Delete the contact and re-add it.  As long as you use the
same name for the contact it will continue to use the
original email address.  To get around this I have to re-
add the contact and spell their name differently.

Regards, Guy