Aster Mail

Judgement

What it is

Complete system

What it does

Hosted email with end-to-end encryption: mail is encrypted on your device, the provider never holds your keys, and the apps are open source.

Adopt it when

You want private email with a free plan and would otherwise look at Proton Mail or Tuta.

Watch out

A new provider with no track record yet; moving email away later means changing your address unless you bring your own domain.

Ready for

Usable

Runs as

Cloud service, mobile app and desktop app

What the license allows

Closed source: you use it under the maker's terms and cannot change or resell the code.

Judged on 2026-11-08 from the maker's description and Wikipedia. The license and age lines are worked out directly.

Open-source alternatives to Aster Mail

1. 1
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2. 2
   Stalwart stalwartlabs

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3. 3
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4. 4
   KumoMTA KumoCorp

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5. 5
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8. 8
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10. 10
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Other commercial email servers and webmail

1. 1
   Gmail (Google Workspace) Google

   Pysy ajan tasalla posteistasi ja pidä yrityksesi turvassa suojatulla, älykkäällä ja helppokäyttöisellä Gmaililla.

   Complete system Production-ready A business wants reliable hosted email with strong spam filtering and works mostly in the browser.

   90k readers a month Since 2004 Commercial
   
2. 2
   Proton Mail Proton AG

   Proton Mail is the world’s largest secure email service with over 100 million users. Available on Web, iOS, Android, and desktop. Protected by Swiss privacy law.

   Complete system Production-ready Privacy is your first concern and you want encrypted email, especially between Proton users.

   12k readers a month Since 2014 Commercial
   
3. 3
   Fastmail Fastmail Pty Ltd

   Fast, private email hosting for you or your business. More productive, lightning fast, simple and built to save you time.

   Complete system Production-ready An individual, family or small business wants fast, private email on its own domain without Google or Microsoft.

   586 readers a month Since 1999 Commercial
   
4. 4
   Microsoft Exchange Online Microsoft

   Complete system Production-ready An organisation uses Outlook and Microsoft 365 and needs shared mailboxes, resource calendars and compliance controls.

   Commercial
   
5. 5
   Zoho Mail Zoho Corporation

   Ad-free Business Email Hosting with a clean, easy-to-use interface. Secure & professional with integrated business Calendar, Contacts, Notes & Tasks.

   Complete system Production-ready A small business wants low-cost email on its own domain, particularly if it uses other Zoho apps.

   Commercial
   

Under it

Every program, Aster Mail included, runs on a microchip.

How compilers were built, back to punched paper tape