The Message Series has many powerful features, which sometimes makes it harder to work out when your message is going to be sent to each contact attached to the series. This article explains how the various dates involved in the series work together. The following diagram will be used to help the explanation:
The overall Message Series Campaign depicted by the grey bar has a start and end date, as does each of the messages that are part of the series. Each person attached to the message series has their own date - referred to as the trigger date. Often when you first create a series you will add a group of contacts to your campaign all at once, giving them a trigger date that causes the first message to go to them straight away. After that, new contacts added to the series are likely to be given a trigger date that coincides with the date that they were added to the series, causing the messages to be sent out in the appropriate staggered fashion.
The diagram above demonstrates some important characteristics of the message series:
In order to receive a particular message, the number of days after your contact's trigger date must fall within the start and end date of that message.
Customer 1 will receive all the messages, but will not receive the 3rd message more than once, despite the 'repeat every 3 months' setting, because the overall campaign ends before that could take effect.
Customer 2 will only receive message 1, because it is due to be sent 1 day after the trigger date, and 1 day after customer 2's trigger date is within the campaign's start and end dates as well as message 1's start and end dates. That's not the case for either message 2 (which ends before customer 2's trigger date), and message 3 (which ends before 14 days after customer 2's trigger date).
The above diagram shows that a message series that ends on a certain date; you can setup your message series without an end date, in which case it will continue to run forever. Similarly your email and SMS messages within the series may also have no end date.
Giving messages end dates is important when the message is date sensitive such as a message promoting a one time event or expiry date.
One person can be added to the message series, more than once, as long as they have different trigger dates each time they are added.
For more about the different uses for a message series, please read: http://help.enudge.com.au/articles/436684-creating-an-enudge-message-series