Warning: This is what happens when you skip QA!
I guess I have become somewhat of a collector of "oops" email messages (see links below). It's become somewhat commonplace to send out an email with an error and then follow up with a correction. But make sure the cure isn't worse than the disease - check out this example from The eMarketing Association that was sent with the subject line "woops". There are three egregious errors in the first two sentences. Woops, indeed.
(Click to enlarge.)