science

Posteo

Posteo is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Posteo rather than just read about it. In short: Posteo is an email service provider based in Berlin, Germany, offering paid email accounts for individuals and businesses. The service gained prominence during the aftermath of the post-2013 global surveillance disclosures, especially for its high standard security features and relative anonymity as it does not require any private information in the registration process.

Key takeaways

Posteo belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Posteo to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Posteo from memory before moving on to harder problems.

Reference excerpt

Posteo is an email service provider based in Berlin, Germany, offering paid email accounts for individuals and businesses. The service gained prominence during the aftermath of the post-2013 global surveillance disclosures, especially for its high standard security features and relative anonymity as it does not require any private information in the registration process. Posteo offers support for DNSSEC/DANE and PGP (through Mailvelope in the web interface, which is running open source Roundcube). Additionally, they offer two-factor-authentication via TOTP, Extended Validation certificates, HPKP for the HTTPS connection, and various themes to choose from, including dark mode. In 2022, Posteo had more than 500,000 active mail accounts.

Data minimization and security

The company advertises its privacy by design. Both registration and payment are possible anonymously, and users' IP addresses are not stored. Data transmissions between customers and the company are consistently encrypted using TLS. Since August 2013, Posteo has supported Perfect Forward Secrecy encryption, both for its own connections and for transmissions to other providers—at the time, it was one of the first German providers to support it for all email protocols. Perfect Forward Secrecy means that a new, random key is generated for each connection, which is then used to encrypt the connection. This prevents the subsequent decryption of intercepted data. Posteo uses Extended Validation certificates to authenticate its servers. Since May 2014, Posteo has supported the DANE/TLSA (DNS-based Authentication of Name Entities) protocol, thereby eliminating various vulnerabilities of TLS encryption, particularly during the transmission of emails between Posteo and other providers. To benefit from the additional security provided by DANE when accessing the site via a browser, a corresponding browser add-on is required. All Posteo servers are located in Germany, and their hard drives are AES-encrypted. Since October 2015, Posteo has been using HTTP Public Key Pinning, a technique employed by websites, to secure the HTTPS connection between the web interface and the user. Since November 2014, webmail access can be further secured by two-factor authentication based on the TOTP standard. To prevent this from being circumvented by email programs using IMAP, POP3, or SMTP, customers can block these accesses upon request. Since May 2015, customers have been able to optionally activate encrypted email storage, so that all emails stored at Posteo are individually encrypted with the customer's (salted) password. Since July 2016, customers have been able to optionally activate the TLS delivery guarantee, so that outgoing emails are only sent to servers of other providers if an encrypted connection is possible. Since August 2016, the webmail interface has displayed whether the transmission path is secured by DANE before emails are sent. The company relies on open standards and free software, including the JavaScript code used on its website and in its webmail. The source code of software that Posteo has co-developed is available under free licenses on GitHub. Against this background, Posteo has criticized the "E-Mail made in Germany" initiative from the outset as a closed, isolated solution. In the 26th activity report of the Federal Commissioner for Data Protection and Freedom of Information, Andrea Voßhoff, published at the end of May 2017, Posteo was praised—without mentioning the company name. Posteo had “implemented data protection […] in a truly impressive way.” At the same time, Posteo published the audit report on which this statement was based, which had been prepared at the end of 2016. Among other things, the report praised the company’s internal, independent data protection officer, who also works in customer support the anonymous payment system, through which Posteo “does not collect any inventory data”; the company’s decision not to store “customer-identifiable IP addresses”; and its multi-layered encryption. In general, Posteo “takes the principle of data minimization very seriously.” At the end of January 2019, the Federal Constitutional Court rejected a constitutional complaint by the email provider Posteo and ruled against Posteo's practice of not storing IP addresses. According to the ruling, an email provider like Posteo must collect IP addresses for the purpose of law enforcement if this has been ordered by a judge.

Support for end-to-end encryption

Since January 2015, the company has offered automatic encryption of incoming emails using either S/MIME or PGP . To use this feature, users must submit their public S/MIME or PGP key to the company. Each email is then encrypted with this key after it arrives. This method does not replace true end-to-end encryption , as emails are only encrypted after they arrive on Posteo's servers, and not at the sender's end. Therefore, even with incoming encryption enabled, Posteo can still check emails for spam, for example. At the end of December 2015, the company released an open-source plug-in for its Roundcube web interface, which facilitates PGP encryption in conjunction with the Mailvelope browser add-on. This includes querying and offering for import public keys obtained from various sources (key servers, listed in DNS as OPENPGPKEY) by Posteo servers. Private keys, plaintext messages, and cryptographic operations always remain under the user's control. Posteo strictly rejects encryption solutions where email providers offer server-side support, deeming them inherently insecure.

Transparency report

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Posteo

Start with the simplest possible case. Write down what Posteo claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Posteo before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Posteo ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Posteo

In research: Posteo appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Posteo in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Posteo is common in secondary-school and first-year university syllabi. It links to neighbouring topics Companies based in Berlin, German companies established in 2009, Internet properties established in 2009, so understanding it makes those chapters shorter.
In everyday life: Look for Posteo outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Posteo in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Posteo means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Posteo out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Posteo in simple terms?

Why does Posteo matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Posteo?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Posteo.