What does your app look like? Provide a screenshot - Don't really have much atm. But the next point may help.
How does the user send an email in your app? - There is a send button at the top of the screen. When a new item is entered by a user, this is then clicked on by a Manager from a Gallery and then clicks another button (if needed) to send the email. Just need something after this point to disable the send button for that item, to stop the email being sent twice?
What data is stored in the gallery? How are you currently tracking if an email has been sent? - I am not at this point.