Reminders can only be configured globally - all invoices use same rules and send time Daily Send Time applies to ALL reminders - cannot stagger different reminder intervals Minute selector only allows 15-minute increments (0, 15, 30, 45) External server processes missions every minute - actual send may be ±1 minute from configured time Reminders don't send for paid invoices - mission automatically cancelled when invoice marked paid No way to send payment reminders for invoices with deleted customers Reminders stop automatically once due date passes (transition to Overdue phase) No built-in email bounce handling or unsubscribe links Portal API client must be configured - without it, missions cannot be scheduled Email subject limited to plain text (no HTML tags or formatting)