I had a guy come over to give us an estimate for some work on our house. He was tethering his phone to his laptop and, when he e-mailed me a file, I kept checking to see if it had come through while he was going through the file with me on his screen.
Having not received the e-mail at the end of his presentation, I asked him to check his Outbox and Sent Items to see where it was in the sending process. He responded, "What do you mean?" so I explained how the e-mail goes into the local Outbox once you hit "send" and stays there until it's fully sent, after which it moves to Sent Items on the server. He had no clue, and when he pulled up his Outbox, there were 20 or so e-mails sitting there dating back over a year.
"Wow, those people are probably wondering why I never got back to them!"
He made some lighthearted comment about "wow, those people are probably wondering why I never got back to them!" I was horrified; not only had his business probably lost these potential customers by never responding to them, these people had a negative experience with his company and could've publicly posted negative customer-service reviews in this age of Angie's List and Yelp. All because some e-mails never made it past this guy's Outbox.
Moral of the story: Know how to use all of your business' tools, even if they're not the tools you specifically use to do the work being paid for.