Insure that you have inserted an unsubscribe link in either the email Stationery, or the HTML Content of your email.

In addition, you'll also want to make sure that you update the plain text of your message and email Stationery. Follow the steps below to update the Plain Text Version of your email and Stationery.

Email Message:
  1. Navigate to Email > select Email Campaigns
  2. Select the Campaigns tab
  3. Find your Email Campaign and click Manage
  4. Select the Messages tab
  5. Find your message and click Edit
  6. Click Plain Text Content
  7. Click Convert to Plain Text
  8. Click Save
Email Stationery:
  1. Navigate to Email > select Stationery
  2. Find the Stationery that your message is using and click Edit
  3. Click Plain Text
  4. Click Update Plain Text
  5. Click Save
You should now be able to approve your message without seeing that error message.