---
meta_title: "비공개 암호화 이메일 서비스 권장 목록 - Privacy Guides"
title: 이메일 서비스
icon: material/email
description: 이러한 이메일 제공 업체는 여러분의 이메일을 안전하게 보관하기에 적합합니다. 대부분이 OpenPGP 암호화를 제공하여 다른 이메일 서비스와도 호환됩니다.
cover: email.webp
global:
  - 
    - randomize-element
    - "table tbody"
---

<small>Protects against the following threat(s):</small>

- [:material-server-network: 서비스 제공자/제공 업체(Service Providers)](basics/common-threats.md#privacy-from-service-providers ""){.pg-teal}

이메일은 모든 온라인 서비스 이용에 사실상 필수적이지만, 개인 간 대화에는 권장드리지 않습니다. 다른 사람에게 연락할 때는 이메일보다는 순방향 비밀성을 지원하는 메신저를 사용하는 것이 좋습니다.

[권장 메신저](real-time-communication.md ""){.md-button}

## 권장 제공 업체

그 외 용도로 이메일을 사용한다면, 지속 가능한 비즈니스 모델을 갖추고 보안 및 프라이버시 기능을 기본 제공하는 이메일 제공 업체를 권장합니다. 자세한 사항은 [전체 평가 기준](#criteria)을 참고해 주세요.

| 서비스 제공자                       | OpenPGP/WKD                            | IMAP / SMTP                                        | Zero-Access Encryption                               | Anonymous Payment Methods             |
| ----------------------------- | -------------------------------------- | -------------------------------------------------- | ---------------------------------------------------- | ------------------------------------- |
| [Proton Mail](#proton-mail)   | :material-check:{ .pg-green }          | :material-information-outline:{ .pg-blue } 유료 요금제만 | :material-check:{ .pg-green }                        | 현금                                    |
| [Mailbox Mail](#mailbox-mail) | :material-check:{ .pg-green }          | :material-check:{ .pg-green }                      | :material-information-outline:{ .pg-blue } Mail only | 현금                                    |
| [Tuta](#tuta)                 | :material-alert-outline:{ .pg-orange } | :material-alert-outline:{ .pg-orange }             | :material-check:{ .pg-green }                        | Monero <br>Cash via third party |

In addition to (or instead of) an email provider recommended here, you may wish to consider a dedicated [email aliasing service](email-aliasing.md#recommended-providers) to protect your privacy. Among other things, these services can help protect your real inbox from spam, prevent marketers from correlating your accounts, and encrypt all incoming messages with PGP.

- [More Information :material-arrow-right-drop-circle:](email-aliasing.md)

## OpenPGP 호환 서비스

These providers natively support OpenPGP encryption/decryption and the [Web Key Directory (WKD) standard](basics/email-security.md#what-is-the-web-key-directory-standard), allowing for provider-agnostic end-to-end encrypted emails. For example, a Proton Mail user could send an E2EE message to a Mailbox Mail user, or you could receive OpenPGP-encrypted notifications from internet services which support it.

<div class="grid cards" markdown>

- ![Proton Mail logo](assets/img/email/protonmail.svg){ .twemoji } [Proton Mail](#proton-mail)
- ![Mailbox Mail logo](assets/img/email/mailbox-mail.svg){ .twemoji } [Mailbox Mail](#mailbox-mail)

</div>

<div class="admonition warning" markdown>
<p class="admonition-title">Warning</p>

When using E2EE technology like OpenPGP your email will still have some metadata that is not encrypted in the header of the email, generally including the subject line! Read more about [email metadata](basics/email-security.md#email-metadata-overview).

OpenPGP also does not support forward secrecy, which means if the private key of either you or the message recipient is ever stolen, all previous messages encrypted with it will be exposed.

- [How do I protect my private keys?](basics/email-security.md#how-do-i-protect-my-private-keys)

</div>

### Proton Mail

<div class="admonition recommendation" markdown>

![Proton Mail 로고](assets/img/email/protonmail.svg){ align=right }

**Proton Mail**은 프라이버시, 암호화, 보안, 사용 편의성에 중점을 둔 이메일 서비스입니다. They have been in operation since 2013. Proton AG is based in Geneva, Switzerland.

The Proton Free plan comes with 500 MB of Mail storage, which you can increase up to 1 GB for free.

[:octicons-home-16: Homepage](https://proton.me/mail){ .md-button .md-button--primary }
[:simple-torbrowser:](https://protonmailrmez3lotccipshtkleegetolb73fuirgj7r4o4vfu7ozyd.onion){ .card-link title="Onion Service" }
[:octicons-eye-16:](https://proton.me/mail/privacy-policy){ .card-link title="Privacy Policy" }
[:octicons-info-16:](https://proton.me/support/mail){ .card-link title="Documentation" }
[:octicons-code-16:](https://github.com/ProtonMail){ .card-link title="Source Code" }

<details class="downloads" markdown>
<summary>Downloads</summary>

- [:simple-googleplay: Google Play](https://play.google.com/store/apps/details?id=ch.protonmail.android)
- [:simple-appstore: App Store](https://apps.apple.com/app/id979659905)
- [:simple-github: GitHub](https://github.com/ProtonMail/android-mail/releases)
- [:fontawesome-brands-windows: Windows](https://proton.me/mail/bridge#download)
- [:simple-apple: macOS](https://proton.me/mail/bridge#download)
- [:simple-linux: Linux](https://proton.me/mail/bridge#download)
- [:octicons-browser-16: Web](https://mail.proton.me)

</details>

</div>

Free accounts have some limitations, such as not being able to search body text and not having access to [Proton Mail Bridge](https://proton.me/mail/bridge), which is required to use a [recommended desktop email client](email-clients.md) (e.g., Thunderbird). 유료 계정에는 Proton Mail Bridge, 추가 저장 공간, 사용자 지정 도메인 지원 등의 기능이 제공됩니다. If you have the Proton Unlimited plan or any multi-user Proton plan, you also get [SimpleLogin](email-aliasing.md#simplelogin) Premium for free.

Proton Mail 앱 [감사 증명서](https://proton.me/blog/security-audit-all-proton-apps)는 2021년 11월 9일에 [Securitum](https://research.securitum.com)에서 발급하였습니다.

Proton Mail has internal crash reports that are **not** shared with third parties. This can be disabled in the web app: :gear: → **All Settings** → **Account** → **Security and privacy** → **Privacy and data collection**.

#### :material-check:{ .pg-green } 사용자 지정 도메인 및 별칭

Proton Mail 유료 이용자는 서비스에서 자신의 도메인을 사용하거나 [Catch-all](https://proton.me/support/catch-all) 주소를 사용할 수 있습니다. Proton Mail also supports [sub-addressing](https://proton.me/support/creating-aliases), which is useful for people who don't want to purchase a domain.

#### :material-check:{ .pg-green } 비공개 결제 수단

Proton Mail [accepts](https://proton.me/support/payment-options) **cash** by mail in addition to standard credit/debit card, [Bitcoin](advanced/payments.md#other-coins-bitcoin-ethereum-etc), and PayPal payments.

#### :material-check:{ .pg-green } 계정 보안

Proton Mail supports TOTP [two-factor authentication](https://proton.me/support/two-factor-authentication-2fa) and [hardware security keys](https://proton.me/support/2fa-security-key) using FIDO2 or U2F standards. The use of a hardware security key requires setting up TOTP two-factor authentication first.

#### :material-check:{ .pg-green } 데이터 보안

Proton Mail은 이메일 및 [캘린더](https://proton.me/news/protoncalendar-security-model)에 [Zero Access Encryption](https://proton.me/blog/zero-access-encryption)을 적용하고 있습니다. Zero Access Encryption으로 보호된 데이터는 여러분 본인만 접근 가능합니다.

[Proton Contacts](https://proton.me/support/proton-contacts) 연락처에 저장된 특정 정보(표시된 이름, 이메일 주소 등)는 Zero Access Encryption으로 보호되지 않습니다. 전화번호 등, Zero Access Encrpytion이 적용된 연락처 필드는 자물쇠 아이콘으로 표시됩니다.

#### :material-check:{ .pg-green } 이메일 암호화

Proton Mail은 웹메일에 [OpenPGP 암호화 기능을 내장](https://proton.me/support/how-to-use-pgp)하고 있습니다. 다른 Proton Mail 계정으로 보내는 이메일은 자동으로 암호화되며, Proton Mail 외 주소로 보내는 이메일에 대한 OpenPGP 암호화는 계정 설정에서 간편하게 활성화할 수 있습니다. Proton also supports automatic external key discovery with WKD. This means that emails sent to other providers which use WKD will be automatically encrypted with OpenPGP as well, without the need to manually exchange public PGP keys with your contacts. They also allow you to [encrypt messages to non-Proton Mail addresses without OpenPGP](https://proton.me/support/password-protected-emails), without the need for them to sign up for a Proton Mail account.

Proton Mail also publishes the public keys of Proton accounts via HTTP from their WKD. This allows people who don't use Proton Mail to find the OpenPGP keys of Proton Mail accounts easily for cross-provider E2EE. This only applies to email addresses ending in one of Proton's own domains, like `@proton.me`. If you use a custom domain, you must [configure WKD](basics/email-security.md#what-is-the-web-key-directory-standard) separately.

#### :material-information-outline:{ .pg-blue } 계정 해지

유료 계정 사용 중에 14일 이상 요금이 [미납된 경우](https://proton.me/support/delinquency), 여러분은 더 이상 자신의 데이터에 접근할 수 없습니다. 30일이 지나면 계정은 연체 상태가 되며, 더 이상 메일을 수신할 수 없습니다. 이 기간 동안에도 계속해서 요금이 청구됩니다. Proton will [delete inactive free accounts](https://proton.me/support/inactive-accounts) after one year. You **cannot** reuse the email address of a deactivated account.

#### :material-information-outline:{ .pg-blue } 추가 기능

Proton Mail's [Unlimited](https://proton.me/support/proton-plans#proton-unlimited) plan also enables access to other Proton services in addition to providing multiple custom domains, unlimited hide-my-email aliases, and 500 GB of storage.

### Mailbox Mail

<div class="admonition recommendation" markdown>

![Mailbox Mail logo](assets/img/email/mailbox-mail.svg){ align=right }

**Mailbox Mail** is an email service with a focus on being secure, ad-free, and powered by 100% eco-friendly energy. 2014년부터 운영되었습니다. Mailbox Mail is based in Berlin, Germany.

Accounts start with up to 2 GB storage, which can be upgraded as needed.

[:octicons-home-16: Homepage](https://mailbox.org){ .md-button .md-button--primary }
[:octicons-eye-16:](https://mailbox.org/en/data-protection-privacy-policy){ .card-link title="Privacy Policy" }
[:octicons-info-16:](https://kb.mailbox.org/en/private){ .card-link title="Documentation" }

<details class="downloads" markdown>
<summary>Downloads</summary>

- [:octicons-browser-16: Web](https://login.mailbox.org)

</details>

</div>

#### :material-check:{ .pg-green } 사용자 지정 도메인 및 별칭

Mailbox Mail lets you use your own domain, and they support [catch-all](https://kb.mailbox.org/en/private/custom-domains/how-to-set-up-a-catch-all-alias-with-a-custom-domain-name) addresses. Mailbox Mail also supports [sub-addressing](https://kb.mailbox.org/en/private/account-article/what-is-an-alias-and-how-do-i-use-it), which is useful if you don't want to purchase a domain.

#### :material-check:{ .pg-green } 비공개 결제 수단

Mailbox Mail doesn't accept any cryptocurrencies as a result of their payment processor BitPay suspending operations in Germany. However, they do accept **cash** by mail, **cash** payment to bank account, bank transfer, credit card, PayPal, and a couple of German-specific processors: Paydirekt and Sofortüberweisung.

#### :material-check:{ .pg-green } 계정 보안

Mailbox Mail supports [two-factor authentication](https://kb.mailbox.org/en/private/account-article/how-to-use-two-factor-authentication-2fa) for their webmail only. You can use either TOTP or a [YubiKey](security-keys.md#yubikey) via the [YubiCloud](https://yubico.com/products/services-software/yubicloud). Web standards such as [WebAuthn](basics/multi-factor-authentication.md#fido-fast-identity-online) are not yet supported.

#### :material-information-outline:{ .pg-blue } 데이터 보안

Mailbox Mail allows for encryption of incoming mail using their [encrypted mailbox](https://kb.mailbox.org/en/private/e-mail-article/your-encrypted-mailbox). 새로 수신하는 메시지는 즉시 공개 키로 암호화됩니다.

However, [Open-Xchange](https://en.wikipedia.org/wiki/Open-Xchange), the software platform used by Mailbox Mail, [does not support](https://kb.mailbox.org/en/private/security-privacy-article/encryption-of-calendar-and-address-book) the encryption of your address book and calendar. A [standalone option](calendar.md) may be more appropriate for that data.

#### :material-check:{ .pg-green } 이메일 암호화

Mailbox Mail has [integrated encryption](https://kb.mailbox.org/en/private/e-mail-article/send-encrypted-e-mails-with-guard) in their webmail, which simplifies sending messages to people with public OpenPGP keys. They also allow [remote recipients to decrypt an email](https://kb.mailbox.org/en/private/e-mail-article/my-recipient-does-not-use-pgp) on Mailbox Mail's servers. OpenPGP가 없어 수신자가 자신의 메일함에서 직접 복호화할 수 없을 경우에 이 기능을 사용할 수 있습니다.

Mailbox Mail also supports the discovery of public keys via HTTP from their WKD. This allows people outside of Mailbox Mail to find the OpenPGP keys of Mailbox Mail accounts easily for cross-provider E2EE. This only applies to email addresses ending in one of Mailbox Mail's own domains, like `@mailbox.org`. If you use a custom domain, you must [configure WKD](basics/email-security.md#what-is-the-web-key-directory-standard) separately.

#### :material-information-outline:{ .pg-blue } 계정 해지

Your account will be set to a restricted user account when your contract ends. It will be irrevocably deleted after [30 days](https://kb.mailbox.org/en/private/payment-article/what-happens-at-the-end-of-my-contract).

#### :material-information-outline:{ .pg-blue } 추가 기능

You can access your Mailbox Mail account via IMAP/SMTP using their [.onion service](https://kb.mailbox.org/en/private/faq-article/the-tor-exit-node-of-mailbox-org). However, their webmail interface cannot be accessed via their .onion service, and you may experience TLS certificate errors.

All accounts come with limited cloud storage that [can be encrypted](https://kb.mailbox.org/en/private/drive-article/encrypt-files-on-your-drive). Mailbox Mail also offers the alias [@secure.mailbox.org](https://kb.mailbox.org/en/private/e-mail-article/ensuring-e-mails-are-sent-securely), which enforces the TLS encryption on the connection between mail servers, otherwise the message will not be sent at all. Mailbox Mail also supports [Exchange ActiveSync](https://en.wikipedia.org/wiki/Exchange_ActiveSync) in addition to standard access protocols like IMAP and POP3.

Mailbox Mail has a digital legacy feature for all plans. You can choose whether you want any of your data to be passed to heirs, providing that they apply and provide your testament. Alternatively, you can nominate a person by name and address.

## 그외 제공자

이 제공자들은 영지식 암호화를 사용하기에 메일을 안전하게 보관하는 용도로 좋습니다. However, they don't support interoperable encryption standards for E2EE communications between different providers.

<div class="grid cards" markdown>

- ![Tuta logo](assets/img/email/tuta.svg#only-light){ .twemoji loading=lazy }![Tuta logo](assets/img/email/tuta-dark.svg#only-dark){ .twemoji loading=lazy } [Tuta](#tuta)

</div>

### Tuta

<div class="admonition recommendation" markdown>

![Tuta logo](assets/img/email/tuta.svg#only-light){ align=right }
![Tuta logo](assets/img/email/tuta-dark.svg#only-dark){ align=right }

**Tuta** (formerly *Tutanota*) is an email service with a focus on security and privacy through the use of encryption. Tuta has been in operation since 2011 and is based in Hanover, Germany.

Free accounts start with 1 GB of storage.

[:octicons-home-16: Homepage](https://tuta.com){ .md-button .md-button--primary }
[:octicons-eye-16:](https://tuta.com/privacy){ .card-link title="Privacy Policy" }
[:octicons-info-16:](https://tuta.com/support){ .card-link title="Documentation" }
[:octicons-code-16:](https://github.com/tutao/tutanota){ .card-link title="Source Code" }
[:octicons-heart-16:](https://tuta.com/community){ .card-link title="Contribute" }

<details class="downloads" markdown>
<summary>Downloads</summary>

- [:simple-googleplay: Google Play](https://play.google.com/store/apps/details?id=de.tutao.tutanota)
- [:simple-appstore: App Store](https://apps.apple.com/app/id922429609)
- [:simple-github: GitHub](https://github.com/tutao/tutanota/releases)
- [:fontawesome-brands-windows: Windows](https://tuta.com/#download)
- [:simple-apple: macOS](https://tuta.com/#download)
- [:simple-linux: Linux](https://tuta.com/#download)
- [:octicons-browser-16: Web](https://app.tuta.com)

</details>

</div>

Tuta doesn't support the [IMAP protocol](https://tuta.com/support#imap) or the use of third-party [email clients](email-clients.md), and you also won't be able to add [external email accounts](https://github.com/tutao/tutanota/issues/544#issuecomment-670473647) to the Tuta app. [Email import](https://github.com/tutao/tutanota/issues/630) is not currently supported either, though this is [due to be changed](https://tuta.com/blog/kickoff-import). Emails can be exported [individually or by bulk selection](https://tuta.com/support#generalMail) per folder, which may be inconvenient if you have many folders.

#### :material-check:{ .pg-green } 사용자 지정 도메인 및 별칭

Paid Tuta accounts can use either 15 or 30 aliases depending on their plan and unlimited aliases on [custom domains](https://tuta.com/support#custom-domain). Tuta doesn't allow for [sub-addressing (plus addresses)](https://tuta.com/support#plus), but you can use a [catch-all](https://tuta.com/support#settings-global) with a custom domain.

#### :material-information-outline:{ .pg-blue } 비공개 결제 수단

Tuta only directly accepts credit cards and PayPal, however [**cryptocurrency**](cryptocurrency.md) can be used to purchase gift cards via their [partnership](https://tuta.com/support/#cryptocurrency) with ProxyStore.

#### :material-check:{ .pg-green } 계정 보안

Tuta supports [two-factor authentication](https://tuta.com/support#2fa) with either TOTP or U2F.

#### :material-check:{ .pg-green } 데이터 보안

Tuta has [zero-access encryption at rest](https://tuta.com/support#what-encrypted) for your emails, [address book contacts](https://tuta.com/support#encrypted-address-book), and [calendars](https://tuta.com/support#calendar). 즉, 계정에 저장된 메시지 및 기타 데이터는 사용자 본인만 읽을 수 있습니다.

#### :material-information-outline:{ .pg-blue } 이메일 암호화

Tuta [does not use OpenPGP](https://tuta.com/support/#pgp). Tuta accounts can only receive encrypted emails from non-Tuta email accounts when sent via a [temporary Tuta mailbox](https://tuta.com/support/#encrypted-email-external).

#### :material-information-outline:{ .pg-blue } 계정 삭제

Tuta will [delete inactive free accounts](https://tuta.com/support#inactive-accounts) after six months. 돈을 지불하면 비활성화된 계정을 재사용할 수 있습니다.

#### :material-information-outline:{ .pg-blue } 추가 기능

Tuta offers the business version of [Tuta to non-profit organizations](https://tuta.com/blog/secure-email-for-non-profit) for free or with a heavy discount.

## 평가 기준

**Please note we are not affiliated with any of the providers we recommend.** In addition to [our standard criteria](about/criteria.md), we have developed a clear set of requirements for any email provider wishing to be recommended, including implementing industry best practices, modern technology and more. We suggest you familiarize yourself with this list before choosing an email provider, and conduct your own research to ensure the email provider you choose is the right choice for you.

### 기술

안전하고 최적화된 서비스를 제공하기 위해서는 이러한 기능이 중요하다고 판단했습니다. You should consider whether the provider has the features you require.

**최소 요구 사항:**

- Must encrypt email account data at rest with zero-access encryption.
- Must be capable of exporting emails as [Mbox](https://en.wikipedia.org/wiki/Mbox) or individual .EML with [RFC5322](https://datatracker.ietf.org/doc/rfc5322) standard.
- Allow users to use their own [domain name](https://en.wikipedia.org/wiki/Domain_name). 사용자 지정 도메인 이름은 서비스가 부실해지거나 프라이버시 보호를 우선시하지 않는 다른 회사에 인수되는 경우에도 에이전시를 유지할 수 있도록 해주기 때문에 사용자에게 중요합니다.
- Must operate on owned infrastructure, i.e. not built upon third-party email service providers.

**우대 사항:**

- Should encrypt all account data (contacts, calendars, etc.) at rest with zero-access encryption.
- Should provide integrated webmail E2EE/PGP encryption as a convenience.
- Should support WKD to allow improved discovery of public OpenPGP keys via HTTP. GnuPG users can get a key with this command: `gpg --locate-key example_user@example.com`.
- 외부 사용자를 위해 임시 메일함을 지원해야 합니다. This is useful when you want to send an encrypted email without sending an actual copy to your recipient. 이러한 이메일은 보통 수명이 제한돼 있으며 이후 자동으로 삭제됩니다. 수신자가 OpenPGP 등의 암호화를 설정할 필요가 없습니다.
- Should support [sub-addressing](https://en.wikipedia.org/wiki/Email_address#Sub-addressing).
- Should allow users to use their own [domain name](https://en.wikipedia.org/wiki/Domain_name). 사용자 지정 도메인 이름은 서비스가 부실해지거나 프라이버시 보호를 우선시하지 않는 다른 회사에 인수되는 경우에도 에이전시를 유지할 수 있도록 해주기 때문에 사용자에게 중요합니다.
- Catch-all or alias functionality for those who use their own domains.
- Should use standard email access protocols such as IMAP, SMTP, or [JMAP](https://en.wikipedia.org/wiki/JSON_Meta_Application_Protocol). Standard access protocols ensure customers can easily download all of their email, should they want to switch to another provider.
- Email provider's services should be available via an [onion service](https://en.wikipedia.org/wiki/.onion).

### 프라이버시

Privacy Guides이 권장하는 제공자들은 최소한의 데이터만을 수집해야 합니다.

**최소 요구 사항:**

- Must protect sender's IP address, which can involve filtering it from showing in the `Received` header field.
- Must not require personally identifiable information (PII) besides a username and a password.
- Privacy policy must meet the requirements defined by the GDPR.

**우대 사항:**

- Should accept [anonymous payment options](advanced/payments.md) ([cryptocurrency](cryptocurrency.md), cash, gift cards, etc.)
- Should be hosted in a jurisdiction with strong email privacy protection laws.

### 보안

Email servers deal with a lot of very sensitive data. We expect that providers will adopt industry best practices in order to protect their customers.

**최소 요구 사항:**

- Protection of webmail with 2FA, such as [TOTP](basics/multi-factor-authentication.md#time-based-one-time-password-totp).
- Zero-access encryption, which builds on encryption at rest. The provider does not have the decryption keys to the data they hold. This prevents a rogue employee leaking data they have access to or remote adversary from releasing data they have stolen by gaining unauthorized access to the server.
- [DNSSEC](https://en.wikipedia.org/wiki/Domain_Name_System_Security_Extensions)를 지원해야 합니다.
- No TLS errors or vulnerabilities when being profiled by tools such as [Hardenize](https://hardenize.com), [testssl.sh](https://testssl.sh), or [Qualys SSL Labs](https://ssllabs.com/ssltest); this includes certificate related errors and weak DH parameters, such as those that led to [Logjam](https://en.wikipedia.org/wiki/Logjam_(computer_security)).
- A server suite preference (optional on TLS 1.3) for strong cipher suites which support forward secrecy and authenticated encryption.
- A valid [MTA-STS](https://tools.ietf.org/html/rfc8461) and [TLS-RPT](https://tools.ietf.org/html/rfc8460) policy.
- Valid [DANE](https://en.wikipedia.org/wiki/DNS-based_Authentication_of_Named_Entities) records.
- Valid [SPF](https://en.wikipedia.org/wiki/Sender_Policy_Framework) and [DKIM](https://en.wikipedia.org/wiki/DomainKeys_Identified_Mail) records.
- Must have a proper [DMARC](https://en.wikipedia.org/wiki/DMARC) record and policy or use [ARC](https://en.wikipedia.org/wiki/Authenticated_Received_Chain) for authentication. If DMARC authentication is being used, the policy must be set to `reject` or `quarantine`.
- A server suite preference of TLS 1.2 or later and a plan for [RFC8996](https://datatracker.ietf.org/doc/rfc8996).
- [SMTPS](https://en.wikipedia.org/wiki/SMTPS) submission, assuming SMTP is used.
- Website security standards such as:
    - [HTTP Strict Transport Security](https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security)
    - [Subresource Integrity](https://en.wikipedia.org/wiki/Subresource_Integrity) if loading things from external domains.
- Must support viewing of [message headers](https://en.wikipedia.org/wiki/Email#Message_header), as it is a crucial forensic feature to determine if an email is a phishing attempt.

**우대 사항:**

- Should support hardware authentication, i.e. U2F and [WebAuthn](basics/multi-factor-authentication.md#fido-fast-identity-online).
- [DNS Certification Authority Authorization (CAA) Resource Record](https://tools.ietf.org/html/rfc6844) in addition to DANE support.
- Should implement [Authenticated Received Chain (ARC)](https://en.wikipedia.org/wiki/Authenticated_Received_Chain), which is useful for people who post to mailing lists [RFC8617](https://tools.ietf.org/html/rfc8617).
- Published security audits from a reputable, third-party firm.
- 버그 바운티 프로그램 또는 체계적인 취약점 공개 프로세스가 있음
- Website security standards such as:
    - [Content Security Policy (CSP)](https://en.wikipedia.org/wiki/Content_Security_Policy)
    - [RFC9163 Expect-CT](https://datatracker.ietf.org/doc/rfc9163)

### 신뢰

You wouldn't trust your finances to someone with a fake identity, so why trust them with your email? We require our recommended providers to be public about their ownership or leadership. We also would like to see frequent transparency reports, especially in regard to how government requests are handled.

**최소 요구 사항:**

- Public-facing leadership or ownership.

**우대 사항:**

- 투명성 보고서를 자주 발간해야 합니다.

### 마케팅

With the email providers we recommend, we like to see responsible marketing.

**최소 요구 사항:**

- Must self-host analytics (no Google Analytics, Adobe Analytics, etc.).
- Must not have any irresponsible marketing, which can include the following:
    - Claims of "unbreakable encryption." Encryption should be used with the intention that it may not be secret in the future when the technology exists to crack it.
    - Guarantees of protecting anonymity 100%. When someone makes a claim that something is 100%, it means there is no certainty for failure. We know people can quite easily de-anonymize themselves in a number of ways, e.g.:
        - Reusing personal information e.g. (email accounts, unique pseudonyms, etc.) that they accessed without anonymity software such as Tor
        - [브라우저 핑거프린팅](https://en.wikipedia.org/wiki/Device_fingerprint#Browser_fingerprint)

**우대 사항:**

- Clear and easy-to-read documentation for tasks like setting up 2FA, email clients, OpenPGP, etc.

### 추가 기능

While not strictly requirements, there are some other convenience or privacy factors we looked into when determining which providers to recommend.
