In short
Spark is a cross-platform mail app from Readdle. Its AI features come with the Plus ($10 a month) and Pro ($20 a month) plans, and Spark's privacy policy says they may use third-party AI providers such as Azure OpenAI, OpenAI, Anthropic and Google Vertex AI, with some data processed on Spark's servers. LocalInbox is Mac-only, runs its AI with Apple's on-device model, has no server of its own, and costs a one-time $19 to $49.
At a glance
| Feature | LocalInbox | Spark |
|---|---|---|
| Price | One-time licence: $19 early access, then $49 | Free plan; Plus $10/month, Pro $20/month (or $99 and $199 a year) |
| Where AI runs | Apple's on-device model, on your Mac | On-device and/or third-party AI providers, per Spark's privacy policy |
| AI usage limits | None: it runs on your Mac | Monthly AI quota |
| Company servers | None: your Mac talks to your provider | Some data processed on Spark's servers when a feature needs it |
| Platforms | Mac | Mac, Windows, iPhone, iPad, Android |
| Team features | No | Yes: shared threads, team inbox |
When LocalInbox is the better choice
- You don't want a subscription for AI features.
- You don't want your mail processed by a cloud AI provider or a mail app's servers.
- You want unlimited AI use: it runs on your own Mac.
When Spark is the better choice
- You need the same mail app on Windows or Android.
- Your team shares and comments on email together.
- You use Outlook or Exchange today.
Sources
Facts about Spark were checked in October 2026 and can change; check its website for current prices and features. Facts about LocalInbox come from its own documentation.
Questions
Does LocalInbox have a free plan like Spark?
LocalInbox has a 7-day free trial with every feature, then a one-time licence. There's no subscription.