You can now send custom messages to anybody that contributes to your campaign. You can add this message when setting up your campaign.
Here is the field you will have to fill out in the campaign form.
Your message will be shown in the email after people contribute to your campaign (regardless whether it is tilted or not).
If you only want to send a message to everybody once your campaign tilted, you can use our older “Contact all contributors” button, and write your message there.