After the first node, it is necessary to add an update node to refresh the info in your Contacts List.
2. Double click on the funnel icon to Configure the filter
3. Assign an Email Opened event and click on save
4. Double click on the update node. Name your step with something relating to status update. Insert a new label and name it something like email_status.
5. Set the value to opened (or similar wording) and click on save
6. Then, you must add another branch of your conversation flow with a timer node
7. Now, you have a new branch with a new step. In your new timer node you must configure the period of time you want the next message to be sent to those contacts that did not open the first communication
8. Double click on the timer new step and put a name to your step like wait N days, then select Specific delay from the Delay Time dropdown menu, and there add the amount of time you want to wait before sending the next message.
9. Add another email node after the timer node.
10. Double click Edit the new email node with the content of the communication you want to share to those contacts that did not open the first email
11. Double click on the funnel icon to open the configuration dialogue
12. Finally, configure the status of the filter by selecting the email_status (or the name of label you chose before) label, with the operator Not equal to and the value opened, (or the name you chose before for the opened status). The second email would be sent, three days after the first email, only if in case the recipient didn't open the first email.