Validating mx record
The most important role of DNS for the majority of us is translating names into IP addresses so that network communications can occur.
For example, when you type your web browser, DNS is used to look up that name to determine the IP address of the server to connect to. So if that is how a simple web browser connection is made, what about when somebody sends email to an @address?
Check the Domains FAQ if you don't find what you're looking for.
Follow these instructions to add and set up your domain in Office 365 so your services like email and Skype for Business Online will use your own domain name.
However, it can occasionally take longer for a change you've made to update across the Internet's DNS system.
If you’re having trouble with mail flow or other issues after adding DNS records, see Troubleshoot issues after changing your domain name or DNS records.
Companies that service large email server farms, such as Google, will have several servers to handle massive amounts of incoming emails.
If you want to learn the full concept about MX-Record, you must need to have basic knowledge about DNS(Domain Name Server/System).
If you don’t have any idea about DNS, then Please visit This link Domain Basics…
The questions which come very first in user’s mind are listed below with proper explanation. When your domain is registered, it’s assigned several DNS records, which enable it to be located on the Internet.
These include MX records, which direct the domain’s mail flow. Log in to Enom administrative console at https://com/by entering your 'Login ID', 'Password' and clicking 'Login'.2. Click the 'Edit' button beside each and set the priority with higher numbers like 10, 20 and so on.