Setting up Proton Mail

Last updated October 2026

Proton Mail encrypts mailboxes end-to-end and therefore does not speak ordinary IMAP to the outside. The bridge between the two worlds is the Proton Mail Bridge: a small program from Proton that runs on your computer, decrypts the mail and offers it to YouniqMail as a local IMAP server.

The Bridge requires a paid Proton plan (Mail Plus, Unlimited, Business, Family or Visionary); the free Proton account does not include it. That is Proton’s decision, not a YouniqMail limitation.

Set up the Bridge

1. Download the Proton Mail Bridge and install it.
2. Start the Bridge and sign in with your Proton account.
3. The Bridge then shows its own credentials: a username and a password generated by the Bridge. You will need both in a moment; they are not your Proton credentials.

The Bridge must be running whenever YouniqMail should fetch mail. Best let it start with the system; the Bridge offers that setting itself.

Set up the account in YouniqMail

1. Settings → Email Accounts → Add Email Account
2. Pick Proton Mail.
3. Enter Your name and your Proton address.
4. Enter Bridge username and Bridge password from the Bridge window.
5. IMAP port and SMTP port are prefilled with the Bridge’s standard ports (1143 and 1025). Only change them if you changed them in the Bridge. The connection always goes to your own computer (127.0.0.1).
6. Test Connection, then Continue and Finish.

Do not use your Proton credentials

The most common mistake: the fields want the credentials the Bridge displays, not those of your Proton account. With the Proton credentials, the connection always fails.

The Bridge certificate

The Bridge secures the local connection with its own self-issued certificate. YouniqMail remembers this certificate on the first connection, without you having to confirm anything, and accepts no other afterwards. That way no other program on your computer can pose as the Bridge.

If the Bridge later presents a different certificate, syncing of the account stops and YouniqMail lets you know. That is normal after you have reinstalled or reset the Bridge. Under Settings → Email Accounts, the account has a Proton Bridge certificate section with the fingerprint of the known certificate. Check again compares it with the certificate the Bridge presents now. With Trust the new certificate you accept the new one. Only do that if you really have reinstalled or reset the Bridge.

Quirks in daily use

Bridge closed = account offline. If the Bridge is not running, the account behaves as if there were no network. First check on connection trouble: is the Bridge started and signed in?

Several Proton addresses: How they arrive in YouniqMail depends on the Bridge’s address mode. In combined mode, all addresses end up in one account. In split mode, the Bridge shows separate credentials for each address, and you set up each address in YouniqMail as its own account.

Changing server and ports: Under Settings → Email Accounts with Change IMAP/SMTP Settings, for example if you have changed the ports or the encryption in the Bridge. The only server allowed there is 127.0.0.1.