After you have created a segment on Aritic PinPoint, Contacts are automatically added into that segment based on the filter conditions that you have laid down while creation of the segment. Sometimes it appears that the number of emails sent to a particular segment in less than the number of contacts that are inside that segment. Don’t worry it is not your fault, this may have occurred due to one of the following reasons.
1. Contacts that bounced when you had sent campaigns earlier, may have got added into the list.
2. Contacts who have unsubscribed out of your prior campaigns and are now under the “Do Not Contact” segment have been added into the Segment.
3. Your contacts may have already received the email in earlier campaigns which is why they did not receive it the second time.