What is Accepted Domains? Basically, to configure your domain names to receive emails. For example, you have a domain name such as www.msinformation.com and you except to receive emails with this address such as firstname.lastname@example.org.
You have to add your domain names to Accepted domain list (can be more than one) and you should create mail address for users.
All you need is to go to mail flow and then to accepted domains
Click on “+” icon and add your domain if it is not listed. As you can see, you have three option to choose. First option is for a user inside of your organization that is chosen, other is relay option.
You can add more than one domain names but you have to choose one of them is default.