It's unusual to have that many calls about email issues when there was actually nothing about them that was due to a technical problem on our end of things. They were almost all ordinary, run-of-the-mill things -- setting up our email in a 3rd-party client, giving the email system a kick in the pants because the address had been created when the MX records were still propagating and therefore weren't quite ready yet, and the like. There were a few that ran me a bit of a merry chase, like the password popup that showed up in the client, which turned out to be a "Sir, when you didn't update the expiration date on your credit card, your email evaporated, so now your Outlook is trying to log in to an email box that doesn't exist. Let's just get this set up again here..." and then the one that by all rights could have been an hour-long screamfest except for the part where he casually mentioned a VPN, and I remembered that VPNs are jealous creatures that don't like other connections, so in under ten minutes (it was more like five) we diagnosed that he needs to have his VPN off before trying to send, and he can still use port 25.
I would say that a good 75% or more of my calls today were email, and there was only one that could have possibly wound up being something on our end that was our responsibility (versus something on our end that was their responsibility, like not getting the bill paid), and even that one was most likely a situation where you just have to wait for the mail server to start serving.