Side by side
Metis Mail vs Mozilla Thunderbird
Both stand on email clients. Which one you can start free with, which one lets you read the code, and what each costs once you pay.
Free plan Open source APISelf-hostedWeb
Choose Metis Mail if you want a unified inbox with an AI agent, phishing analysis, and a free forever open-source plan. Teams that need shared mailboxes, team rules, or priority support can choose Workspace; people who need native iOS or Android apps may want to wait for those apps to arrive.
Visit Metis Mail
Free plan Open source AndroidLinuxMac+1
Thunderbird combines multi-account email with calendar, contacts and task tools, with desktop offline access and message scheduling. It is free and open-source, with Android listed for mobile use.
Visit Mozilla ThunderbirdThe facts
| Metis Mail | Mozilla Thunderbird | |
|---|---|---|
| Free plan | Yes | Yes |
| Open source | Yes | Yes |
| Runs on | API, Self-hosted, Web | Android, Linux, Mac, Windows |
| Lowest paid plan | Cloud Pro annual: $115 per user a year | Free or on request |
| Plans published | 8 | 2 |
| Maker | Metis Mail | Mozilla Thunderbird |
| Website | trymetis.email | thunderbird.net |
| On email clients | #2 of 142 | #1 of 142 |
Metis Mail: what it does well
- Combines Gmail, Microsoft 365, and Zoho Mail accounts in one inbox.
- Keeps folders, threads, attachments, and read states synchronized.
- AI agent summarizes threads, drafts replies, and triages messages.
- Phishing verdicts include a risk score and reasons.
- Free plan includes every feature, unlimited workspaces, and mailboxes.
What to know first
- Cloud Pro allows up to three connected mailboxes.
- Native iOS and Android apps are on the roadmap.
- Workspace costs $20 a month.
Mozilla Thunderbird: what it does well
- Unified inbox or separate account management
- Includes calendar, contacts and tasks
- Desktop supports offline access and scheduled sending
- Open-source and free forever
- Third-party add-ons and interface customization
What to know first
- Android is the only listed mobile platform
Alternatives to Metis Mail Alternatives to Mozilla Thunderbird The whole list