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Proton Mail Bridge IMAP and SMTP settings

By Julien CoulaudPublished November 1, 20264 min read

Proton Mail encrypts mail end to end, so desktop apps such as Outlook, Thunderbird and Apple Mail cannot talk to Proton's servers directly. Proton Mail Bridge sits in between on your computer and handles both directions. These are the settings Proton documents, checked on Proton's support pages on November 1, 2026.

Julien Coulaud on X

Founder of Shipmail, the email platform for businesses and their AI agents. Every guide here draws on mail servers running in production.

  • Proton Mail
  • Proton Mail Bridge
  • IMAP
  • SMTP

Short answer

Proton Mail Bridge runs a local mail server, so the IMAP and SMTP server in your email app is 127.0.0.1, with IMAP on port 1143 and SMTP on port 1025 by default. Use the username and password shown in Bridge under Mailbox details, not your Proton account password. Bridge needs a paid Proton plan and must be running while the app is open.

Proton Mail Bridge settings

ProtocolServerPortEncryption
IMAP, incoming (through Bridge)Sources[5]Proton: Proton Mail Bridge new Outlook for macOS setup guide[3]Proton: fix the IMAP or SMTP port error in Proton Mail Bridge[7]Proton: comprehensive guide to Bridge settings127.0.0.11143 by defaultSTARTTLS or SSL, as set in Bridge
SMTP, outgoing (through Bridge)Sources[5]Proton: Proton Mail Bridge new Outlook for macOS setup guide[3]Proton: fix the IMAP or SMTP port error in Proton Mail Bridge[7]Proton: comprehensive guide to Bridge settings127.0.0.11025 by defaultSTARTTLS or SSL, as set in Bridge
SMTP submission, sending only[9]smtp.protonmail.ch587STARTTLS, with an SMTP token

Why Proton Mail needs Bridge

In desktop email apps, Proton says Bridge manages both the incoming and outgoing server connections. Bridge is a desktop app that connects to your Proton account and exposes it to your email app as an IMAP and SMTP server on your own machine, at the loopback address 127.0.0.1. Traffic between Bridge and the app gets its own TLS layer, with a self-signed certificate Bridge creates at first setup.Sources[2]Proton: IMAP, SMTP, and POP3 setup[1]Proton Mail Bridge[8]Proton: Proton Mail Bridge connection issues with Thunderbird, Outlook, and Apple Mail

  • Plans: Bridge is available only with a paid plan that includes Proton Mail. Free accounts cannot use it.
  • Apps: Proton names Outlook, Apple Mail and Thunderbird. It says the new Outlook for macOS is not officially supported and recommends Legacy Outlook, Apple Mail or Thunderbird.
  • POP3: not supported. Use IMAP through Bridge.
  • Bridge must be running: if Open on startup is off in Bridge, start Bridge before your email app.
Sources[1]Proton Mail Bridge[2]Proton: IMAP, SMTP, and POP3 setup[5]Proton: Proton Mail Bridge new Outlook for macOS setup guide[7]Proton: comprehensive guide to Bridge settings

Proton Mail Bridge IMAP and SMTP settings

  • IMAP server: 127.0.0.1, port 1143 by default
  • SMTP server: 127.0.0.1, port 1025 by default
  • Encryption: STARTTLS or SSL, whichever is set in Bridge. Proton's Outlook guide uses TLS for both
  • Username: the username shown in Bridge under Mailbox details
  • Password: the password shown in Bridge under Mailbox details, for both incoming and outgoing mail
Sources[5]Proton: Proton Mail Bridge new Outlook for macOS setup guide[3]Proton: fix the IMAP or SMTP port error in Proton Mail Bridge[7]Proton: comprehensive guide to Bridge settings[4]Proton: Proton Mail Bridge Outlook 2013 for Windows setup guide

Copy the values from Mailbox details rather than typing them from a guide. If you changed a port or the connection mode in Bridge, Mailbox details shows the current one, and Proton's setup guides all point back to it.Sources[4]Proton: Proton Mail Bridge Outlook 2013 for Windows setup guide[6]Proton: Proton Mail Bridge Thunderbird setup guide

The Bridge password is not your Proton password

Proton's setup guides say not to use your regular Proton Mail account details in the email app. Your Proton account password goes into Bridge only, when you sign in to it. The email app gets the separate username and password that Bridge shows under Mailbox details.Sources[4]Proton: Proton Mail Bridge Outlook 2013 for Windows setup guide[6]Proton: Proton Mail Bridge Thunderbird setup guide

  1. Step 1

    Install and sign in to Bridge

    Install Proton Mail Bridge on the computer and sign in with your Proton account.

  2. Step 2

    Open Mailbox details

    In Bridge, open your account and find Mailbox details. It shows the server, ports, username and password for your email app.

  3. Step 3

    Add the account in your app

    Choose manual setup if the app offers it, then enter the Mailbox details values for both incoming and outgoing mail.

  4. Step 4

    Accept Bridge's certificate

    Thunderbird and some other apps ask you to confirm a security exception for Bridge's local certificate, once for IMAP and once for SMTP on the first send.

Sources[4]Proton: Proton Mail Bridge Outlook 2013 for Windows setup guide[6]Proton: Proton Mail Bridge Thunderbird setup guide[8]Proton: Proton Mail Bridge connection issues with Thunderbird, Outlook, and Apple Mail

Sending from apps and devices with an SMTP token

Bridge only runs on a computer. For a device or a business application that only needs to send, Proton offers SMTP submission with a token instead. Proton's support page says it is available on paid Proton Mail plans with custom domain addresses, and its setup overview describes it as a business plan feature.Sources[9]Proton: set up SMTP to use business applications or devices with Proton Mail[2]Proton: IMAP, SMTP, and POP3 setup

  • Server: smtp.protonmail.ch
  • Port: 587 with STARTTLS, or TLS if STARTTLS is not offered
  • Authentication: PLAIN or LOGIN
  • Username: the custom domain address you chose for the token
  • Password: the SMTP token. Your login and mailbox passwords do not work here
[9]

Create the token in Proton Mail on the web under Settings, All settings, IMAP/SMTP, SMTP tokens, then Generate token. Proton shows it once, so copy it before you close the window. Make one token per app, so deleting one stops only that app. SMTP submission sends only; receiving mail in an app still needs Bridge.[9]

Common Proton Mail Bridge problems

  • Port already occupied: another app holds 1143 or 1025. In Bridge's advanced settings, change the default port up by one, such as 1144 or 1026, and repeat until the error stops. Then update the port in your email app.
  • The app rejects your password: you entered your Proton account password. Use the password from Mailbox details.
  • The app cannot reach 127.0.0.1: check that Bridge is running, and that the server and ports in the app match Mailbox details. If Open on startup is off, Bridge does not start with the computer.
  • Bridge failed to connect to your email client: remove the account from the email app, remove it from Bridge to clear its cache, sign in to Bridge again and redo the setup.
  • Sending fails on the first message in Thunderbird: confirm the security exception for the SMTP certificate, then send again.
Sources[3]Proton: fix the IMAP or SMTP port error in Proton Mail Bridge[4]Proton: Proton Mail Bridge Outlook 2013 for Windows setup guide[8]Proton: Proton Mail Bridge connection issues with Thunderbird, Outlook, and Apple Mail[6]Proton: Proton Mail Bridge Thunderbird setup guide[7]Proton: comprehensive guide to Bridge settings

If you are deciding between Proton Mail and Shipmail for a team, the comparison page covers that. This page only covers connecting the Proton account you have.

Using a mailbox on your own domain instead

With Proton, every desktop app goes through Bridge on each computer, and phones use Proton's own app. A mailbox that speaks IMAP and SMTP directly connects from any app on any device without a local helper, though it does not give you Proton's end-to-end encryption.

A Shipmail mailbox on your own domain works in the same apps with one set of settings: server mx1.shipmail.to, IMAP on port 993 with SSL/TLS, SMTP on port 465 with SSL/TLS or 587 with STARTTLS, and your full address as the username. Plans start at $4 a month for 2 mailboxes. It is not free, and it only makes sense if you want an address you own rather than one tied to a provider.Sources[10]Shipmail email client connection settings[11]Shipmail pricing

Sources11 sourcesVerified 2026-11-01
  1. [1]
    Proton Mail Bridge

    Proton Mail Bridge is a desktop app that connects email clients such as Outlook, Thunderbird and Apple Mail to a Proton account over IMAP and SMTP through a local server. It is available only with a paid plan that includes Proton Mail.

    proton.me · 2026-11-01

  2. [2]
    Proton: IMAP, SMTP, and POP3 setup

    In desktop email apps, Proton Mail Bridge manages the incoming and outgoing server connections. Bridge is currently available only with a paid Proton Mail plan. POP3 is not supported. SMTP submission lets business plans send from business applications and devices.

    proton.me · 2026-11-01

  3. [3]
    Proton: fix the IMAP or SMTP port error in Proton Mail Bridge

    Bridge uses port 1143 for IMAP and 1025 for SMTP by default. When another app holds one, Bridge shows a port error; change the default ports in Bridge's advanced settings, raising the number by one (1144, 1026) until the error stops, and update the email client to the new port.

    proton.me · 2026-11-01

  4. [4]
    Proton: Proton Mail Bridge Outlook 2013 for Windows setup guide

    Enter the server information from Bridge with IMAP port 1143 and SMTP port 1025, and make sure the encrypted connection type is TLS for both. Do not use the regular Proton Mail account details: use the username and password shown in Bridge under Mailbox details, for both incoming and outgoing mail.

    proton.me · 2026-11-01

  5. [5]
    Proton: Proton Mail Bridge new Outlook for macOS setup guide

    The SMTP outgoing server and IMAP incoming server should be 127.0.0.1. Use the account details from Bridge under Mailbox details, not the regular Proton Mail account details. The new Outlook for macOS is not officially supported; Proton recommends Legacy Outlook, Apple Mail or Thunderbird.

    proton.me · 2026-11-01

  6. [6]
    Proton: Proton Mail Bridge Thunderbird setup guide

    Enter the password shown in Bridge Mailbox details, not the regular account password. Thunderbird asks to confirm a security exception for Bridge's local certificate on IMAP, and again for SMTP on the first send; send a test message, confirm the exception and send again.

    proton.me · 2026-11-01

  7. [7]
    Proton: comprehensive guide to Bridge settings

    Bridge runs IMAP and SMTP servers on the device whose default ports can be changed, and its connection to the email client can be switched between STARTTLS and SSL. If Open on startup is off, Bridge must be started before the email client. Export TLS certificates lets you trust Bridge's certificate manually.

    proton.me · 2026-11-01

  8. [8]
    Proton: Proton Mail Bridge connection issues with Thunderbird, Outlook, and Apple Mail

    Bridge talks to the email client over the local loopback interface 127.0.0.1 and adds a TLS layer with a self-signed certificate created at first setup. When Bridge reports it failed to connect to the email client, remove the account from the client, remove it from Bridge to clear its cache, sign in again and redo the setup.

    proton.me · 2026-11-01

  9. [9]
    Proton: set up SMTP to use business applications or devices with Proton Mail

    SMTP submission is available on paid Proton Mail plans with custom domain addresses. Generate a token in Settings, All settings, IMAP/SMTP, SMTP tokens, choosing a custom domain address. Host smtp.protonmail.ch, port 587, PLAIN or LOGIN authentication, STARTTLS (TLS if STARTTLS is not offered). The token is shown once; use one per client. Login and mailbox passwords do not work. SMTP only sends; receiving in a client needs Bridge.

    proton.me · 2026-11-01

  10. [10]
    Shipmail email client connection settings

    Shipmail IMAP, SMTP, and JMAP settings: mx1.shipmail.to, IMAP on port 993 with SSL/TLS, SMTP on port 465 with SSL/TLS or 587 with STARTTLS, the full email address as username, and the mailbox password or an app password.

    shipmail.to · 2026-10-15

  11. [11]
    Shipmail pricing

    Shipmail plan prices, mailbox limits, team access, and send limits.

    shipmail.to · 2026-10-15

Questions worth answering

Common questions about proton mail bridge settings.

What are the Proton Mail Bridge IMAP and SMTP settings?
Server 127.0.0.1, IMAP port 1143 and SMTP port 1025 by default, with the username and password from Bridge's Mailbox details. Encryption is STARTTLS or SSL, as set in Bridge.Sources[5]Proton: Proton Mail Bridge new Outlook for macOS setup guide[3]Proton: fix the IMAP or SMTP port error in Proton Mail Bridge[7]Proton: comprehensive guide to Bridge settings
Can I use Proton Mail in Outlook without Bridge?
Not for reading mail. Proton says Bridge manages the incoming and outgoing connections in desktop apps. Paid plans with a custom domain address can send through smtp.protonmail.ch with an SMTP token, but receiving still needs Bridge.Sources[2]Proton: IMAP, SMTP, and POP3 setup[9]Proton: set up SMTP to use business applications or devices with Proton Mail
Is Proton Mail Bridge free?
No. Bridge is available only with a paid plan that includes Proton Mail, so Proton Free accounts cannot use it.[1]
Which password do I use for Proton Mail Bridge?
The password shown in Bridge under Mailbox details, not your Proton account password. Your account password is only entered in Bridge itself.Sources[4]Proton: Proton Mail Bridge Outlook 2013 for Windows setup guide[6]Proton: Proton Mail Bridge Thunderbird setup guide
Does Proton Mail support POP3?
No. Proton does not support POP3. Use IMAP through Bridge instead.[2]

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