When you press Send Campaign, Sprwt counts the final recipients and adds them to the emails you have already sent this calendar month. If that total reaches your plan's monthly maximum, the campaign is not saved and a modal titled Error - Please upgrade appears: This campaign exceeds the limit of the email available on your plan! Please upgrade in order to continue. The modal contains the same plan picker as the Billing page so you can upgrade on the spot, then send again.

Options: upgrade to a higher tier, reduce the audience (use Don't send to exclusions or a smaller list), or wait until the next month when usage resets.