Twice in the past month we received panicked calls from clients - "Help! Our email stopped working and we can't get any emails!" It turns out in both cases, the problem was the result of someone making updates to a web site and making unintended changes to DNS.
While it's not important for users to know what all the tech jargon means, its VERY important to never make changes that you don't understand. DNS stands for Domain Name Service. It's the database of addresses that make the Internet work. If you type www.ekaru.com into a browser, it's the master directory that tells your computer what IP address to find us at ("A" record"). If you send an email to firstname.lastname@example.org, then a different IP address is used to find us ("mx" record"). Your computer understands IP address, not names.
Your domain name registration establishes the legal ownership of your domain name. You should double check that the registration is in the name of your company or an owner of the business, and not any other employee or outside consultant.
Your name servers tell the world where your IP addresses are stored, so people can find you when they look up your domain name. The most common mistake we see, is that when people make changes to their website without understanding how DNS works they often change their name servers without realizing that the "mx" records will break and mail won't be delivered. It's ok to change name servers, but you must then copy your custom DNS records from your old name servers.
As a general rule, NEVER make changes to DNS unless you 100% understand what you're doing. If someone else is working on your web site, make sure they understand your DNS records before giving them access to your registration.
By the way, the tool we use to check DNS records (and highly recommend!) is www.dnsstuff.com. It's the first place we look when we get a call from a customer who can't access their email when their Internet access is working fine.