Sorry it didn't work out

I seem to have a problem sending emails of late. Several have been bounced back to me for various reasons. For example, "We're sorry. There's a problem with the e-mail address(es) you're trying to send to. Please verify the address(es) and try again. If you continue to have problems, please contact Customer Support."

But this particular one made me laugh: "Hi. This is the qmail-send program. I'm afraid I wasn't able to deliver your message to the following addresses. This is a permanent error; I've given up. Sorry it didn't work out."