You can control the number of email notifications you receive for activity you follow in the community by clicking on your Preferences (drop down menu for your Avatar/Photo).
There are three Inbox stream options that are typically turned on. If you do not visit the community regularly keep turned on the " Inbox - Social activity directed to you such as @mentions, shares, and messages" so that you don't miss any activity directed to you when you are not visiting the community. If you have created any custom activity streams, those will also show up and you will have the option to receive email notifications for them as well.
The Community Digest option will provide a summary of the relevant community activity. To keep up to date with the community activity, it is recommended to receive the digest weekly.
Here is a more thorough explanation of what the different settings mean.
Note: Your replies to email notifications received from the community will be sent to the community. These replies will be created as comments to the conversation threads and placed directly in the community in the appropriate place.