You won't be able to achieve this using network communication protection rule.
Because this rule works at network level and the connection is established between your machine and mail gateway, regardless of the destination, you won't be able to differenciate. The only rule that allows you to allow specific domains is the E-mail protection rule, which works only with Microsoft Outlook, or Lotus Notes.
Hi and thanks for the reply. I know that I can't achieve this functionality using Network rule. My question was about supported email clients. This is enough for me.