If you use a Mac at your desk and an iPhone or iPad everywhere else, the question with any paid app is whether you are buying it once or three times, and whether the smaller devices get the real thing or a cut-down version. This post explains how mailin's Universal Purchase works, what is identical across devices, what stays on each device, and where the operating system version changes which AI features you get.
How Universal Purchase works
mailin is sold as a Universal Purchase on the App Store: you buy it once and use it on Mac, iPhone and iPad. Whether you choose a Personal or Professional subscription or a lifetime one-time purchase, it is tied to your Apple ID and usable on all your devices signed in to that ID. There is no mailin account layered on top; the App Store is the only account involved.
There is one price list, in US dollars on the App Store. Personal is $4.99 per month, $44.99 per year or $99.99 lifetime. Professional is $9.99 per month, $79.99 per year or $249.99 lifetime. Lifetime purchases never renew. The free tier is available on every device with no payment information required. For what each tier includes, see the tier comparison or the pricing section.
The same engine on every device
mailin is one app, built natively in Swift and SwiftUI for all three platforms. The same hand-written parsers handle .mbox, .eml, .emlx, .msg, .pst, .ost and .nsf on iPhone and iPad as on the Mac, with the same format auto-detection and drag-and-drop or file-picker import. The same streaming ingest drains messages in batches of 200 to keep peak memory flat, and the same year-sharded full-text index with BM25 ranking serves search. The interface is localized in the same eleven languages.
The on-device AI engines are likewise the same on all three: Apple Intelligence for summaries, questions and reasoning, and Apple NaturalLanguage for sentiment, language detection and named-entity recognition. Which of those is available depends on the OS version, covered below, not on which device you bought first.
Your archive stays on each device
This is the part to understand before you expect a mailbox imported on the Mac to show up on the iPhone. mailin uses Apple's iCloud to sync settings only. Your archive, index and AI outputs are not synced anywhere, and there are no third-party servers involved at all. If you want the same archive on two devices, import the mailbox file on each of them.
That is a deliberate consequence of the privacy design: no account, no cloud copy of your mail, and nothing leaving the device by default. On the Mac, the data lives in ~/Library/Application Support/com.ecosanskriti.mailin/, and it can be cleared at any time from Settings. Encrypted storage (AES-256) and a biometric lock with Touch ID or Face ID are available for sensitive archives. The privacy post covers the full design.
Requirements by platform
mailin runs on macOS 14.6 or later on both Apple Silicon and Intel Macs, iOS 17.6 or later, iPadOS 17.6 or later, and visionOS 1.3 or later. The App Sandbox applies on all of them, and the app only touches files you explicitly select.
The one thing that differs by OS version is Apple Intelligence. Its features require macOS 26 or later, or iOS 26 or later, on a device that supports Apple Intelligence. On an older system, mailin falls back to NaturalLanguage: sentiment, language detection and entity extraction keep working, but the AI Assistant's written answers, the Thread Story narrative and the AI Digest are not available until the device meets the requirement. Every AI output carries a tag naming the engine that produced it, so you can tell which was used. As with any AI feature, outputs can be inaccurate or incomplete and should be verified against the underlying emails. The on-device AI post has the details.
Family Sharing, Restore Purchases and managing the subscription
mailin supports Family Sharing, so a purchase can be shared with members of your family group through Apple. On a new device, or after reinstalling, use Restore Purchases in the app to bring the purchase across; nothing needs to be re-entered because the entitlement lives with your Apple ID.
Subscriptions auto-renew unless cancelled at least 24 hours before the end of the current period, and they are managed through Apple rather than through mailin: System Settings, then Apple ID, then Subscriptions. Refunds also go through Apple at reportaproblem.apple.com. Purchase verification through StoreKit is one of only two things in the app that can use the network; the other is the optional, off-by-default Cloud AI mode that uses your own API key.
Trying it on each device
The free tier works the same on every device: up to 500 emails, all import formats, basic search and filters, headers and attachments, analytics, on-device sentiment and topic analysis, and three AI assistant queries plus three AI smart-filter queries. You can also try it with sample data before importing anything of your own. Because purchases restore from your Apple ID, it makes sense to test on whichever device is handy and buy once you know it fits. The App Store listing is the same for all three platforms.
FAQ
If I buy on my Mac, do I pay again on my iPhone?
No. mailin is a Universal Purchase tied to your Apple ID. Sign in with the same ID on the iPhone, open the app and use Restore Purchases if it does not pick up the entitlement automatically.
Will my imported archive sync to my other devices?
No. Only settings sync, through Apple's iCloud. The archive stays on the device where you imported it, so import the mailbox file on each device where you want it.
Why do AI summaries work on my Mac but not on an older iPad?
Summaries, question-answering and the Thread Story narrative use Apple Intelligence, which needs macOS 26 or later or iOS 26 or later on a supported device. Sentiment, language detection and entity extraction through NaturalLanguage work on every supported device.