How do I buy Spanbox Pro, and where's the upgrade button?

Upgrade on the pricing page at spanbox.co/pricing, or from the in-app prompt you get when you go past 3 apps. Pick Pro (monthly or yearly) or the one-time Lifetime, pay, and unlimited apps plus the deeper inbox features unlock right away on the same install.

Your setup carries straight over, upgrading just lifts the limit on the install you already have, so every app you've added stays exactly where it is.