science

Mailto

Mailto 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 Mailto rather than just read about it. In short: mailto is a Uniform Resource Identifier (URI) scheme for email addresses. It is used to produce hyperlinks on websites that allow users to send an email to a specific address directly from an HTML document, without having to copy and enter it into an email client.

Key takeaways

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

Reference excerpt

mailto is a Uniform Resource Identifier (URI) scheme for email addresses. It is used to produce hyperlinks on websites that allow users to send an email to a specific address directly from an HTML document, without having to copy and enter it into an email client. It was originally defined by Request for Comments (RFC) 1738 in December 1994, expanded by RFC 2368 in July 1998, and refined by RFC 6068 in October 2010.

Syntax Mailto URIs are composed of the scheme mailto: and zero, one, or more recipient addresses separated with a comma. Additionally, email headers such as cc or subject can be added as attribute-value pairs in the query component of the email. Percent-encoding must be used for the local-part of the Email addresses and for the header values. The Domain parts of the addresses can also be encoded using percent-encoding but using IDNA-Encoding is recommended for interoperability with legacy software.

Examples "mailto" can be used within an HTML document to generate a link for sending email:

Clicking on the hyperlink automatically opens the default email client, with the destination email address pre-filled. It is possible to specify initial values for headers (e.g. subject, cc, etc.) and message body in the URL. Blanks, carriage returns, and line feeds cannot be directly embedded but must be percent-encoded:

Multiple addresses can be specified:

The address can be omitted:

Only the initial header should be prepended with a question mark. All subsequent headers require an ampersand. If this convention is not followed, the scheme will not properly copy over the headers to the email client.

Security and privacy

A number of security issues are mentioned in RFC 6068, one of them being robotic address harvesting. Mailto constructs are locatable within HTML pages by automated means which typically include the use of DOM constructs or regular expressions. Addresses harvested by such means are liable to be added to spammers' mass-mailing lists and thus to receive large amounts of unwanted mail. While methods exist to "harden" mailto links against harvesting—address munging and JavaScript-based address obfuscation among them—these protections can be circumvented by sufficiently sophisticated harvesting robots. Other techniques, like walling the address behind a CAPTCHA or similar "humanity check", provide security on par with that available for other contact methods, most notably web forms, which experience similar challenges with preventing spam.

References

Worked examples

Example 1 — a first encounter with Mailto

Start with the simplest possible case. Write down what Mailto 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 Mailto 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 Mailto 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 Mailto

In research: Mailto 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 Mailto 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: Mailto is common in secondary-school and first-year university syllabi. It links to neighbouring topics Email, URI schemes, Web 1.0, so understanding it makes those chapters shorter.
In everyday life: Look for Mailto 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 Mailto in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Mailto 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 Mailto out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Mailto in simple terms?

Why does Mailto 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 Mailto?

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 Mailto.