If you downloaded Direct Mail from the Mac App Store, then all in-app purchases (e.g. email credits) are handled via the App Store. When you make a purchase, a status window will appear that shows you the current status of your purchase as it is being processed by the App Store and linked to your Direct Mail account:
What to do if an error is encountered during the processing of your payment
If any errors are encountered during the processing of your payment, an error message will appear in the status window. In most cases, the error message will explain the nature of the problem and may include instructions on what you can do to resolve the problem. A "Try Again" button may also appear.
If you quit Direct Mail or turn off your computer before the error has been resolved, don't worry. The next time you open Direct Mail, it will automatically resume processing any payments that have not been completed.
If the Try Again button or the instructions given in the status window don't seem to resolve the issue, please try quitting and re-opening Direct Mail. It will automatically resume processing any payments that have not been completed. You can also try restarting your Mac and then re-opening Direct Mail.
If you are still unable resolve the issue, please contact our support team.