To delete a scheduled send, go to PoliteMail > Campaigns > Scheduled Sends. Click on the message you want to delete. Click the X button next to "Actions" to delete the Scheduled Send.
When you delete a scheduled send, it will prevent the email from going out.
You can also disable a send if you need to stop it. Please note that you can not do this if the message is already in the process of being sent.
To disable a send, click the Edit button. In the second column with the envelop and clock icon, UNcheck the box. This will disable the send. Your message will still be there and you can enable it by checking it again once you are ready for it to go out. If it's past the message's scheduled send time, it will send out immediately.