Side by side
Exo vs Sylpheed
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 Mac
Exo combines AI inbox organization, drafting, calendar access, offline work, and extensibility in a macOS client. Its local storage approach is clear, but using provider-based AI can send email content through the provider selected with your API key.
Visit Exo Free plan LinuxMacWindows
Sylpheed provides a focused, free desktop mail client with extensive protocol, filtering, storage, and external-command support. Its older stable release and discontinued mailing list are important considerations.
Visit SylpheedThe facts
| Exo | Sylpheed | |
|---|---|---|
| Free plan | Yes | Yes |
| Open source | Not published | Not published |
| Runs on | Mac | Linux, Mac, Windows |
| Lowest paid plan | Free or on request | Free or on request |
| Plans published | 1 | 1 |
| Maker | Not published | Not published |
| Website | exo.email | sylpheed.sraoss.jp |
| On email clients | #61 of 142 | #57 of 142 |
Exo: what it does well
- Free macOS plan
- AI priority and drafting
- Gmail and Google Calendar connection
- Offline queued actions
- Local email and token storage
What to know first
- macOS only
- Requires a Gmail account
- Requires an Anthropic API key
- AI may send content to configured providers
Sylpheed: what it does well
- Works offline on major desktop systems
- Supports POP3, IMAP4rev1, SMTP, and NNTP
- Optional GnuPG signing and encryption
- Searches can become folders
- Translated into 30 languages
What to know first
- Stable version dates to January 2018
- Mailing list discontinued in 2025
- Attachment plugin requires 7-Zip and Sylpheed 3.5.1+