Proton Mail Server Settings: IMAP, SMTP and POP3

Everything you need to connect Proton Mail to a mail client, in one place. If you only need one half of the configuration, the dedicated IMAP and SMTP guides cover each in more depth — this page is the quick reference plus the context that makes the values make sense.

All Proton Mail server settings

Before you start

• Requires: Proton Mail Bridge, available on paid plans only
• Why localhost: Bridge runs on your machine and decrypts locally, so clients connect to 127.0.0.1 rather than a Proton server
• Credentials: Bridge issues its own username and password — not your Proton login

IMAP or POP3?

Choose IMAP unless you have a specific reason not to. IMAP synchronises: your mail stays on the server, and every device sees the same mailbox. Read a message on your phone and it shows as read on your laptop. Move it to a folder and it moves everywhere. Delete it and it is gone everywhere.

POP3 works the other way around. It downloads messages to one machine and, by default, removes them from the server afterwards. That behaviour made sense when storage was expensive and most people had a single computer, and it still suits a specific case — archiving mail permanently to your own machine. On any account used from more than one device it causes lasting confusion, because mail collected by one device simply is not there for the others.

Matching ports to encryption

Ports and encryption methods are paired, and mixing them is the single most common reason a correct-looking configuration refuses to connect. Port 993 expects SSL/TLS for IMAP. Port 995 expects SSL/TLS for POP3. Port 587 expects STARTTLS for SMTP, while port 465 expects SSL/TLS for the same job. Take a port from one pairing and encryption from another and the connection fails with an error that usually blames the network or your credentials, sending you looking in entirely the wrong place.

Never configure a mail client without encryption. An unencrypted connection sends your password across the network in a form anyone on the same network can read, and most providers now refuse such connections outright — which is a good thing, even when it is briefly inconvenient.

Common mistakes

Beyond port mismatches, three errors come up repeatedly. Using your website password where the provider requires a generated app password — the client will report the credentials as wrong, which is technically true and entirely unhelpful. Leaving outgoing authentication switched off, which lets mail arrive but never send. And letting the client's automatic setup choose POP3 when you wanted IMAP, which quietly removes mail from the server before you notice.

If something is not working, change one setting at a time and test in between. Changing three things at once and finding it works tells you nothing about which one mattered — and you will be back here the next time you set up a device.