Not exactly a client story but in the same ballpark.
My student is furious with me. Why wasn't I responding to her emails? I check my
mailboxes and find no emails from her. I email her to say that I've received no
emails from her. She sends more emails. She is more furious that I don't answer
them. In the next class, I have her log into her mail account via the web. I check
her Outbox. There's the problem.
"Mary, I can't receive emails from you if you mail them to yourself. Try putting my
email address in the 'TO' box."