Have you set up a series that you are no longer using? Follow these steps to Deactivate your Autoresponder Series.
After logging into your account, go to Contacts and then click the Autoresponder link to view all of the series that you have. If your series has emails that are in a Scheduled State, click Actions to the right and choose to Change Schedule. You will then choose Change to Draft for Editing. This will take the email you have selected and deactivate it. Then repeat this process for all emails within a series that you want to Deactivate or Stop.
You can then also turn the Status of the whole series to off. From the gray bar showing the title of your series click Actions on the right, then choose to Turn off series.
On the next screen you will need to check off that the two conditions are ok to turn off the series.