Email server settings
Proton Mail IMAP settings for Bridge and SMTP submission
The Proton Mail IMAP settings only work through Proton Mail Bridge, a desktop app for paid plans: your mail app connects to 127.0.0.1, IMAP port 1143 and SMTP port 1025, with the user name and password that Bridge shows. To send from a device or business app without Bridge, Proton offers SMTP submission: smtp.protonmail.ch, port 587, STARTTLS, with an SMTP token.
Last checked October 10, 2026, against Proton’s own documentation.
Proton Mail IMAP and SMTP servers
| Server, port and securityServer | Port and security | Sign-in |
|---|---|---|
| IMAP · incoming127 | 1143STARTTLS | Bridge login |
| SMTP · outgoing127 | 1025STARTTLS | Bridge login |
| SMTP · outgoingsmtp | 587STARTTLS | SMTP token |
User name: Bridge: the user name and password from Mailbox details in Bridge, not your Proton password. SMTP submission: the SMTP user name and token you generate for a custom domain address.
Proton Mail Bridge IMAP and SMTP settings
Proton stores your mail with end-to-end or zero-access encryption, and IMAP and SMTP “aren’t designed to access emails stored using zero-access encryption”. Proton’s conclusion: “you can’t configure your client to connect directly with Proton Mail” (Why you need Bridge). Instead, Proton Mail Bridge “encrypts and decrypts your mail as it enters and leaves your computer” (Proton). Mail apps on the same computer connect to it through the loopback address 127.0.0.1 (Proton).
- Paid plans, desktop only. Bridge is available only with a paid Proton Mail plan, on macOS, Windows and Linux, “but not on mobile devices”.
- Ports 1143 (IMAP) and 1025 (SMTP) are Bridge’s defaults. If another program already uses one, Bridge shows an “IMAP or SMTP port error”. Change the port under Settings → Advanced settings → Default ports → Change (Proton suggests one higher, such as 1144 or 1026) and enter the new port in the mail app (Proton).
- STARTTLS or SSL. Bridge encrypts the local connection with a self-signed certificate it generates on first setup (Proton). You switch the protocol between STARTTLS and SSL in Bridge’s settings; the mail app must use the same mode.
- No POP3. Proton says: “We do not offer POP3 support.” Bridge can still download all your mail into a client, for example to export it.
Proton Mail SMTP settings without Bridge
Printers, CRMs and other business apps that only send can use SMTP submission: server smtp.protonmail.ch, port 587, STARTTLS, authentication PLAIN or LOGIN. If an app has no STARTTLS option, Proton calls TLS “the next best option”. Things to know:
- It is available on paid Proton Mail plans with custom domain addresses, and every token belongs to one active custom domain address.
- It only sends. To receive mail in another client you still need Bridge.
- Messages sent this way are not end-to-end encrypted (Proton stores them with zero-access encryption), they appear in your normal Sent folder, and they follow your domain’s SPF record, DKIM record and DMARC settings.
Bridge password and SMTP tokens
Neither route accepts your Proton account password in the mail app.
Bridge password. Open Bridge, select your account and open Mailbox details. Copy the password shown there into the mail app. If the app stores separate passwords for the incoming (IMAP) and outgoing (SMTP) server, enter the same Bridge password in both. After you remove and add the account again in Bridge, use the latest password from Mailbox details (Proton).
SMTP token for SMTP submission (Proton):
- Sign in to Proton Mail in a browser and open Settings → All settings → IMAP/SMTP → SMTP tokens.
- Click Generate token, enter a name and select an active custom domain address.
- Confirm with your Proton account password.
- Copy the SMTP user name and the token. Proton shows the token only once.
Proton recommends a different token for each client, so you can revoke one without cutting off the others.
Set up Proton Mail in Thunderbird and Outlook
Start Bridge and sign in first; the mail app can only connect while Bridge is running.
Thunderbird (Proton’s guide):
- Proton asks you to turn off the experimental Account Hub first: Menu → Settings → General, clear “Create accounts in the new Account Hub”.
- Choose Menu → New Account → Email.
- Enter your name, your Proton address and the Bridge password, then click Continue. Thunderbird usually reports “Configuration found at email provider”. For a custom domain address, choose Configure manually and copy the values from Mailbox details.
- Click Done and confirm the security exception for IMAP. Bridge’s certificate isn’t signed by a certificate authority, so Thunderbird asks.
- Send a test message and confirm the exception for SMTP as well. If an error appears afterwards, dismiss it and send again.
Outlook on Windows (Proton’s guide): add the account manually as POP or IMAP with the server information from Bridge, the user name and password from Bridge (“Do not use your regular Proton Mail account details”), port 1143 for IMAP and 1025 for SMTP, and TLS as the encrypted connection type for both. Turn on SMTP authentication with the same Bridge login.
iPhone and Android: Bridge doesn’t run on mobile devices, so phone mail apps can’t reach Proton Mail over IMAP. Use the Proton Mail app.
Common Proton Mail Bridge errors
| Error or symptom | Fix |
|---|---|
| “Invalid password”, “Authentication failed”, “Login failed” or “Username or password is incorrect” | The app uses your Proton account password or an old Bridge password. Copy the current password from Mailbox details in Bridge, for IMAP and SMTP. |
| IMAP or SMTP port error (port already occupied) | Another program uses port 1143 or 1025. Raise the port in Bridge under Settings → Advanced settings → Default ports and enter the same port in the mail app. |
| “Bridge failed to connect to your email client” | Remove the account from the mail app, remove it from Bridge and sign in again to clear Bridge’s cache, then repeat the setup (Proton). |
| Thunderbird hangs at “Checking mail server capabilities” | Make the connection security in Thunderbird match Bridge, remove all certificate entries for 127.0.0.1 in Thunderbird and trust the new one. Proton’s fallback: STARTTLS in Bridge and None in Thunderbird; the connection from Bridge to Proton’s servers “is always secured with TLS” (Proton). |
| SMTP submission rejects the login | Use the SMTP user name and token that belong together, and send from the custom domain address the token was created for. Your Proton password doesn’t work here, and a deleted token stops working. |
A message that bounces from someone else’s server comes back with a reply code; the SMTP error codes reference explains them.
Is @proton.me a valid email domain?
Yes. A Proton Mail address can end in one of four domains (Proton):
| Domain | Who has it |
|---|---|
proton.me | Default for new accounts |
protonmail.com | Selectable at sign-up instead of proton.me |
pm.me | Paid plans |
protonmail.ch | Proton’s original domain, default for accounts from before 2016 |
All four use the settings on this page. More about the domain itself: is proton.me a legit email. A valid domain says nothing about a single mailbox; check one address with is this a real email address.
Sources
Checked on October 10, 2026. Server names, ports and sign-in rules come from these official pages:
- Proton: IMAP, SMTP, and POP3 setup
- Proton: Why you need Proton Mail Bridge
- Proton: How to set up SMTP to use business applications or devices with Proton Mail
- Proton: How to fix “IMAP or SMTP port error” on Proton Mail Bridge
- Proton Mail Bridge connection issues with Thunderbird, Outlook, and Apple Mail
- Proton: Comprehensive guide to Bridge settings
- Proton: Invalid password error while setting up email client
- Proton Mail Bridge Thunderbird setup guide
- Proton Mail Bridge Microsoft Outlook for Windows setup guide
- Proton: How to resolve issues with “Checking mail server capabilities” notice in Thunderbird
- Proton Mail email domains
Other mailbox providers
Proton Mail settings: FAQ
What are the Proton Mail IMAP settings?
127.0.0.1, port 1143, STARTTLS or SSL (whichever is set in Bridge), with the user name and password from Mailbox details in Bridge. Bridge needs a paid plan and runs on macOS, Windows and Linux.What are the Proton Mail SMTP settings?
127.0.0.1, port 1025, with the same Bridge login. Without Bridge, SMTP submission (paid plans with a custom domain): smtp.protonmail.ch, port 587, STARTTLS, with an SMTP user name and token.Can I use Proton Mail with IMAP without Bridge?
Does Proton Mail support POP3?
Why doesn’t my Proton password work in Outlook or Thunderbird?
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{
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"tag": "",
"domain": "emailvalidation.io",
"format_valid": true,
"mx_found": true,
"smtp_check": true,
"catch_all": null,
"role": true,
"disposable": false,
"free": false,
"score": 0.64,
"state": "deliverable",
"reason": "valid_mailbox",
"did_you_mean": ""
}