If you send emails to the same contacts too often, chances are that they'll feel overwhelmed and unsubscribe, or your emails will be flagged as spam.
If you're selecting campaign recipients and choose any contacts, Tags or Audiences that you email frequently, we'll alert you.
When this happens, we suggest that you consider refining your recipients (maybe updating your Tags and Audiences), which will reduce the amount of contacts you'll reach, but will also make the content you send each of your contacts even more relevant and personal.
Relevant, regulated emails should result in improved contact relationships, increasing trust and loyalty. This tells your contacts that you know what they want and when they want to hear from you, and more importantly, when they don't.