ActiveSync is enabled on our Professional email hosting plan. In a nutshell, it allows you to receive instant email notifications when your messages hit the mail server.
To help you better understand what this means, consider the notifications you receive the moment you receive a text message or a message on a service like Facebook Messenger. Rather than checking for messages at a set interval, your phone will deliver these notifications the moment you receive the message.
ActiveSync works in the same way. It ensures that you are notified as soon as new emails hit your inbox. Your phone will deliver these push notifications so you won’t ever miss a time sensitive email.