Hi there, we are developing a multi-account mail client called Epistles, and I’d really like Proton users here to give some feedback.
The Proton integration works without Bridge. It uses Proton’s API directly, with on-device OpenPGP. Right now it supports:
- SRP login (including two-password mode)
- TOTP 2FA
- Inbox + system folders + custom labels
- Sending to Proton recipients and external PGP recipients
- Multiple addresses on one Proton account
Sensitive key material (mailbox passphrase / private keys) stays in the local OS keychain on each device. It is intentionally excluded from Epistles’ optional cross-device credential vault.
Important caveats up front:
- This Proton API path is reverse-engineered (similar risk profile to Hydroxide / proton-api-client): if Proton changes internals, this can break until we fix it.
- Hardware key login (WebAuthn/U2F) is not implemented yet. TOTP backup is required for now.
- Proton Calendar does not have a native adapter yet but we're working on it.
- Product is closed-source and paid (with a generous free tier).
I know closed-source is a deal-breaker for some people, and that’s fair. If you prefer open implementations, Thunderbird/Hydroxide are solid options.
What I’m specifically looking for from this sub:
If you’ve used Proton Bridge for a long time, what concrete pain points should I design around before wider release?