Auto-Print ProtonMail Emails (Bridge Required)

ProtonMail (now Proton Mail) is end-to-end encrypted, which is great for privacy and a problem for IMAP — Proton's web/app uses Proton's own protocols, and standard IMAP clients can't talk directly to Proton's servers.

The fix is Proton Bridge: a small app from Proton that runs locally and translates between Proton's encrypted protocol and standard IMAP. With Bridge running, AutoPrintEmail talks to localhost; localhost (Bridge) talks to Proton.

Here's the setup, with the constraints up front.

Table of Contents

• What You Need First
• Step 1: Install Proton Bridge
• Step 2: Install AutoPrintEmail
• Step 3: Connect via IMAP to localhost
• Step 4: Filter Rule + Printer
• The Bridge Constraint
• Where Proton Auto-Print Makes Sense
• Where It Doesn't
• Common Issues
  • "Connection refused" from AutoPrintEmail to localhost
  • Bridge keeps logging out
  • Emails not showing up
  • PDF attachments arrive but won't print

What You Need First

• A paid Proton Mail plan (Plus, Professional, Visionary, or any business tier). Bridge is not available on the free tier.
• Proton Bridge installed on the same computer that'll run AutoPrintEmail.
• ~10 minutes for first-time setup.

If you're on the free Proton tier, you'll need to upgrade or pick a different email provider. There's no workaround.

Step 1: Install Proton Bridge

Download from proton.me/mail/bridge for your OS.

Install. Sign in with your Proton account credentials. Bridge will sync your mailboxes locally — first sync can take 5-15 minutes for large mailboxes.

When Bridge finishes initializing, it shows you a set of Bridge IMAP credentials: a hostname (127.0.0.1), port, username (your Proton email), and a password (Bridge-generated, NOT your Proton password). Copy these.

Step 2: Install AutoPrintEmail

Download AutoPrintEmail for the same machine that's running Bridge. Bridge has to be running on the same computer — it only talks to localhost.

Step 3: Connect via IMAP to localhost

In AutoPrintEmail: Add Account → IMAP / POP3.

Use the Bridge credentials:

• Host: 127.0.0.1 (or localhost)
• Port: the port Bridge shows (commonly 1143 or 1144; varies by version).
• Encryption: STARTTLS (Bridge requires it on the local connection).
• Username: your Proton email.
• Password: the Bridge password (the one Bridge generated, not your Proton password).

Connect. AutoPrintEmail logs into Bridge, Bridge talks to Proton, your folders show up.

Step 4: Filter Rule + Printer

Same patterns as any other provider:

• From contains: [your accounting tool / shipping platform / etc.]
• Has attachment: yes
• Action: Print attachment to [your printer]

Pick your printer. Test with one email. Done.

The Bridge Constraint

Proton Bridge must be running for AutoPrintEmail to receive new emails. If Bridge stops, AutoPrintEmail's connection to localhost drops; emails queue up in Proton's servers but never get printed until Bridge is running again.

In practice this means:

• Set Bridge to launch at login (Bridge has this option in its preferences — turn it on).
• Don't quit Bridge "to save memory." It's only ~100MB of RAM and the local sync is lightweight.
• If your machine reboots, Bridge auto-starts and AutoPrintEmail reconnects.

If Bridge crashes or stops syncing for any reason, the AutoPrintEmail dashboard will surface a connection error after a couple of failed polls.

Where Proton Auto-Print Makes Sense

• Privacy-first businesses that chose Proton for the encryption guarantees but still need printed copies of contracts, invoices, etc.
• Regulated industries (legal, healthcare, journalists) using Proton for client confidentiality.
• Anyone running a small office on a paid Proton plan who doesn't want to migrate email providers just to get auto-print.

Where It Doesn't

• Free Proton tier. No Bridge access; no IMAP. Migrate to a paid plan or use a different provider.
• Mobile-only setups. Bridge doesn't run on iOS/Android.
• Server-side / cron-style automation. Bridge wants to run on a desktop with a real GUI; it's awkward on a headless server.

Common Issues

"Connection refused" from AutoPrintEmail to localhost

Bridge isn't running, or the port doesn't match. Open Bridge → check the IMAP credentials shown there. Update AutoPrintEmail's settings to match.

Bridge keeps logging out

Proton sometimes invalidates Bridge sessions when you change your Proton password or revoke devices. Re-sign in to Bridge and copy the new IMAP password into AutoPrintEmail.

Emails not showing up

Bridge syncs your Proton inbox to a local cache. New emails appear in the cache only after Bridge polls Proton (usually within a minute). If a specific email isn't appearing, check the Proton webmail to confirm it actually arrived; if it did and Bridge isn't seeing it, restart Bridge.

PDF attachments arrive but won't print

Proton encrypts attachments end-to-end. Bridge decrypts on the local machine. Once decrypted, the PDF is identical to any other PDF — AutoPrintEmail prints it normally. If a specific PDF won't print, it's almost always a printer driver issue (try opening the PDF in Preview/Acrobat first to confirm it renders).