Proton Mail Alternatives That Support IMAP Directly

Proton Mail is private, but it does not speak IMAP the way the rest of the internet does. To use a normal client — Thunderbird, Apple Mail, Outlook, or an AI-native inbox — you install a small local app called Proton Bridge, log Bridge into your Proton account, and point the client at a Bridge address on localhost. Bridge runs only on macOS, Windows and Linux, and it only runs on paid Proton plans. On a phone, on a Chromebook, at a work machine you cannot install software on, that whole flow is a dead end.

This page lists the private email providers that support IMAP directly — no bridge, no localhost, no proxy — with an honest note about what each one gives up in exchange. The point is not to talk anyone out of Proton. The point is to answer the reader who has already decided that a native IMAP connection is a hard requirement and now wants a mailbox that offers it without asking them to run a second program.

The short answer#

If you want private email that speaks IMAP the moment you plug in an address and a password, the standard pick is Fastmail — long-established, IMAP native, and the vendor that co-authored JMAP for clients that want something better than IMAP. It is not encrypted at rest the way Proton advertises, and it sits under Australian jurisdiction, so those are the trades to accept.

For readers who care most about server-side encryption at rest of message bodies — Proton's headline claim — the honest concession is that no general-purpose IMAP provider matches Proton's model, because encryption at rest and IMAP access from any client push in opposite directions. Mailbox.org and Posteo come closest, both offering optional PGP integration on top of native IMAP, but you accept a hybrid: your inbox is legible to a standard client, and the encryption sits at the message layer rather than the mailbox layer.

We build AI Emaily, and we are not a mail provider — we are the client you connect to any of the providers below. This page ranks providers because that is what the query is asking; the client layer is covered in its own section further down, disclosed as ours.

Why does Proton need Bridge in the first place?#

Proton stores message bodies encrypted with keys the user controls, so the server holds ciphertext it cannot read. IMAP was designed decades earlier to move plain, server-readable messages between a mail store and a client, and it assumes the server can see what it is serving. Those two designs do not meet naturally.

Bridge is Proton's answer. It is a small program that runs on the user's machine, holds the account credentials in an OS keychain, decrypts messages locally, and then republishes them over an IMAP endpoint on 127.0.0.1 so a regular client can read them. In effect, Bridge is a personal, single-user IMAP server that lives on the same computer as the client.

The practical consequences are the ones this page is answering. Bridge needs a running desktop OS, which rules out iOS, Android, iPad, Chromebook and any locked-down work laptop. Bridge is only available on Proton Mail Plus and higher, so it is not an option on the free plan. And any client that expects to reach a real mail server over the public internet — a mobile mail app, a webmail-style front end, a hosted third-party tool — cannot see a Bridge running on the user's laptop.

How we compared#

Every option below was checked against the vendor's own current documentation for IMAP support, protocol coverage, jurisdiction and encryption model. We describe packaging shape — free tier, trial, per-seat, usage-metered — and send the reader to the live pricing page for numbers, because private-mail pricing has moved several times in the past year and a printed figure would already be stale by the time a reader arrives here.

The criteria that actually decide a Proton-to-somewhere-else move are these: does IMAP work directly from any client on any device, without a bridge or a browser; where does the provider sit legally; what encryption is offered and at what layer; is there a migration path off Proton that preserves folders and dates; and what does the free or entry tier look like when you have not yet committed. Feature lists past those points tend to be tie-breakers, not deciders.

Private IMAP providers at a glance#

Read the last column twice — it is where the trade sits. Every row supports IMAP with a normal address and password on a paid plan; the row for AI Emaily is included at the end because it is the client layer the reader will need after picking one, and we build it.

Fastmail#

Fastmail is the default answer for anyone leaving Proton because native IMAP is the requirement. It has been an independent mail company for more than two decades, its team co-authored the JMAP standard as a modern replacement for IMAP, and it exposes both — so a client that wants IMAP works, and a client that wants faster sync over JSON works too. On the desktop, Apple Mail, Thunderbird, Outlook, Mimestream and AI Emaily all connect with a normal address and an app-specific password.

The trade to accept is the one Fastmail is upfront about: your message bodies are stored on Fastmail's servers in a form Fastmail can read. That is what makes native IMAP work from any client on any device without a bridge, and it is the opposite of Proton's zero-access design. If a legal request lands on a Fastmail server, encrypted-at-rest as marketed by Proton is not the shield. Encryption at rest as offered by Fastmail is disk-level, not per-message.

Fastmail also sits under Australian jurisdiction, which is a factor for some threat models and not others. It is worth reading their transparency reports and the current position on the Assistance and Access Act before assuming European-style protection, and it is the reason the readers who prioritise legal jurisdiction sometimes step past Fastmail to a German or Swiss option below.

Packaging is a simple monthly or annual per-mailbox subscription with a free trial — no free tier — and pricing has held steady in the market for a long time. Verify the current numbers on their site before you commit.

Mailbox.org#

Mailbox.org is a Berlin-based provider built around a stricter privacy stance than most general-purpose IMAP hosts, and it is the one to look at first for a reader whose real preference was Proton's threat model but whose real requirement is IMAP without a bridge. Native IMAP, POP3, SMTP, CalDAV and CardDAV all work with standard clients out of the box; no bridge, no browser required.

Where it gets closer to Proton's story is in what you can bolt on. Mailbox.org runs an integrated OpenPGP layer that can encrypt inbound mail on arrival with a key you control, and offers a paid guard-mailbox add-on for readers who want the on-server encryption story tightened further. None of this is transparent the way Proton is — you do have to set it up, and it interacts with IMAP in the ways PGP interactions always do (encrypted bodies are still encrypted to your client, and search over encrypted content is limited).

Jurisdiction is Germany, and the company has a public track record on transparency reports and lawful-access pushback. Packaging is a modest monthly fee per mailbox with a 30-day free trial rather than a permanent free plan, and custom domains, aliases and cloud storage are included at reasonable tiers. Check the current tier layout on the vendor page before you migrate.

Posteo#

Posteo is the German provider that treats privacy as a product decision rather than a marketing surface. Signup is deliberately anonymous, payment can be made in cash by post, no ads, no tracking, and the business is funded entirely by user subscriptions rather than any adjacent product. Native IMAP, POP3, SMTP, CalDAV and CardDAV all work from any client.

The unusual piece is what Posteo calls crypto-mailstorage: an on-server encryption layer that, when turned on, encrypts message headers, bodies and attachments at rest with a key derived from your login password. That is not zero-access encryption — Posteo could technically observe mail passing through before storage — but it is meaningfully further than most IMAP providers go, and it works transparently with a normal IMAP client.

The obvious constraint is that Posteo does not offer custom domains at all. You get an address at posteo.de (or one of the localised TLDs), and that is deliberate — the argument is that hosting the domain elsewhere leaks metadata that undermines the rest of the model. If you need to keep an existing custom domain, Posteo is not for you. If you are willing to switch to a posteo.* address for a personal mailbox, it is one of the cheapest and most consistent private options in this list.

Runbox#

Runbox is a small Norwegian provider that has been quietly running since 1999. It supports IMAP, POP3, SMTP, CalDAV and CardDAV natively, sits under Norwegian jurisdiction (outside the EU, no Five Eyes membership), and is powered by Norwegian hydro rather than the usual data-centre mix — a positioning point they make openly and one that matters to some readers.

The tone of the product is the opposite of Fastmail's polish. The web client is functional, not fashionable; feature velocity is not the point. What Runbox is actually selling is long-term stability, a genuinely small privacy-first operator, and a mailbox that will still be there and still work the same way in ten years. For readers who felt Proton's slick surface was a distraction from the boring durability they actually wanted, Runbox reads as a lower-key answer to the same question.

Packaging is a per-mailbox subscription with a trial, aliases and custom domains at reasonable tiers, and a fair amount of storage per plan. Encryption follows the standard IMAP-provider pattern — TLS in transit, at-rest server storage, optional PGP layered by you — so it does not match Proton's zero-access claim. If that is a hard requirement, Mailbox.org or Posteo are the closer picks.

StartMail#

StartMail is a Dutch provider from the team behind the Startpage search engine, and its pitch is privacy plus aliases plus built-in PGP. Native IMAP and SMTP work with any standard client on any paid plan, so the reader who wants to keep using Apple Mail or Thunderbird — or connect a modern AI-native client — can do so with a normal address and an app-specific password.

Where StartMail leans is the alias system. You can create disposable addresses on the fly and route them all into one mailbox, which is how many privacy-first users handle newsletters, one-off signups and vendors they do not trust with a stable address. The built-in PGP tools make sending an encrypted message to another PGP user straightforward without an add-on client.

Jurisdiction is the Netherlands, which sits under EU privacy law. Packaging is a flat monthly or annual per-mailbox subscription with a trial rather than a free tier; custom domains are supported on the higher tier. The web interface is functional rather than delightful; if the client-side experience matters most, plan on pairing StartMail with a strong IMAP client rather than living in the webmail.

Kolab Now#

Kolab Now is a Swiss-hosted groupware suite built on the Kolab open-source stack — mail, calendar, contacts, files, chat and video, delivered as a single hosted bundle. Native IMAP works out of the box, and Kolab is one of the few providers on this list that also speaks JMAP through the Cyrus JMAP implementation, which matters if you want an IMAP fallback plus a modern client that can use JMAP for faster sync.

The reason to pick Kolab is not the mail on its own; on that dimension Fastmail is smoother and Mailbox.org is cheaper. The reason to pick it is if you want a Proton-alternative-plus-everything-else — a Swiss-hosted, open-source groupware suite that replaces the Google Workspace or Microsoft 365 you might otherwise stitch together — and you want IMAP as a way to connect any mail client you already trust.

Jurisdiction is Switzerland, which has its own set of legal considerations distinct from EU jurisdictions and is often cited alongside Germany for privacy-conscious hosting. Encryption is standard TLS-in-transit and at-rest server storage — no zero-access. Packaging is per-user monthly with a group plan for teams; check the current tiers before you commit.

Zoho Mail#

Zoho Mail is the outlier on this list and it earns its place for a specific reader: someone who wants a private-ish mailbox on a custom domain at the lowest sustainable price and does not consider India a red line for jurisdiction. Native IMAP is available on the paid plans, and Zoho's Mail Suite plans include the wider Zoho office bundle if you want it.

The privacy story is thinner than the European providers above — Zoho is an ad-free mail product, not a zero-access one, and it does not attempt Proton's threat model. But it is genuinely private in the ordinary sense: no ads scanning mail contents, no data sold, an EU data-residency option available for accounts that request it, and a business that funds itself through the wider Zoho product line rather than through your inbox.

The trade-off is scale-of-vendor: Zoho is a large multi-product company rather than a single-purpose mail specialist, so the mail product moves at the pace of a large roadmap. For a reader who is prioritising a working IMAP mailbox on a custom domain over a small privacy-first team, that is a reasonable trade. For a reader whose real preference was the boutique feel of Proton, it is not.

AI Emaily — the client layer, disclosed#

The order matters here: pick the provider first, then pick the client. AI Emaily is the client. We are not a mail provider, and we would be lying if we ranked ourselves at the top of a provider roundup — the reader who arrived on this page is looking for a mailbox, and the honest top pick for that is Fastmail. We build AI Emaily, and this section is the disclosure.

Where AI Emaily fits is the sentence after: once you have picked a provider from the list above, you point AI Emaily at it over IMAP and get an AI-native inbox on top — triage, semantic search, replies drafted in a voice you set through a Personal Context brain and per-contact profiles, and Copilot mode that always requires human approval before sending. Autopilot is available for the routine actions you explicitly allow, and every action is undoable and audited.

AI Emaily runs against Gmail, Outlook and any IMAP account, so all seven providers above work. It runs as a real downloadable desktop app on macOS (Apple Silicon only) and Windows, a native iOS app, and a web app in any modern browser; on Android it is a PWA rather than a native app today. The privacy posture is compatible with the reason someone leaves Proton in the first place: OAuth tokens and message bodies are encrypted at rest, model providers see nothing that is used for training, and BYOK is available if you want your own model key.

That is the whole placement. One client section, one disclosure line, one link — the rest of the page is about the providers, because the providers are the answer to the question the reader typed.

How to choose for your situation#

The chooser below is deliberately short. Most readers do not need eight rows of scoring; they need to know which one row is theirs.

1. 1

   You just want native IMAP and do not want to think about it

   Fastmail. It is the most polished IMAP provider on this list, it also speaks JMAP if you have a client that wants it, and it works with any mail client on any device. Accept that it is not encrypted-at-rest the way Proton advertises.

2. 2

   You picked Proton for the zero-access encryption specifically

   Mailbox.org or Posteo. Neither matches Proton's model, but both let you layer PGP or on-server encryption on top of a native IMAP mailbox, which is the closest a general-purpose provider can get without becoming Proton.

3. 3

   You want the smallest, most privacy-quiet vendor

   Runbox in Norway or Posteo in Germany. Both are small operators with long track records, transparent business models and no adjacent products funding the mailbox.

4. 4

   You want a whole groupware suite, not just mail

   Kolab Now. Mail is one component; calendar, contacts, files and chat are the rest of the reason to pick it, and IMAP plus Cyrus JMAP means any client you already trust still connects.

5. 5

   You want a mailbox on a custom domain for as little as possible

   Zoho Mail. The privacy story is thinner than the European providers but the price and custom-domain support are the strongest on this list.

6. 6

   You want disposable aliases as a first-class feature

   StartMail. Aliases and built-in PGP are what the product is actually organised around, and native IMAP means you can drive it from any client.

What migration off Proton actually looks like#

The mechanical part is simpler than most people expect. Every provider on this list supports IMAP, so migrating means running an IMAP-to-IMAP transfer of the mailbox from Proton (through Bridge, one last time) into the new provider. Folders, dates and read state generally carry across; labels do not always survive, because IMAP folders are hierarchical and Proton's labels are not exactly folders.

The part people underestimate is the address itself. If you have been using an @proton.me or @pm.me address publicly, moving providers means either taking a new address (and updating everywhere it is used) or moving your custom domain (if you were on a paid plan that supported one). The custom-domain path is easier — point the MX records at the new provider — but it does require you were already using one on Proton.

Once the mailbox lands, the last step is the client. If you are staying on Thunderbird or Apple Mail, the connection is a standard IMAP account. If you are moving to an AI-native client, connect that too and let it index; see the connect-imap doc for the settings shape each provider uses.