Checks last time email was created for this piece of data (e.g Order ID, Customer ID) and excludes any that the age is less than this value. If the field is blank, no repetition is allowed.

Autoresponder Max has pre-built filtering to help remove any duplication of emails.  The Don't Repeat ID Within controls how often the customer is allowed to be emailed regarding the specific data (e.g. an order).  The value represents how long after the last email can the customer be contacted again, but not the customer, but the data the email campaign uses.  If the email campaign uses an order and value is set to 1 Days, that means only after 1 day has passed can order be reused by the email campaign.

Having a value of blank means there will never be any repetition and having a value of 0 Minutes means repetition will be allowed every time.

NOTE: In some scenarios, deleting any data on your store and re-adding may cause this setting to work incorrectly.