Address munging

Address mungingis the practice of disguising ane-mail addressto prevent it from being automatically collected by unsolicited bulk e-mail providers. Address munging is intended to disguise an e-mail address in a way that prevents computer software from seeing the real address, or even any address at all, but still allows a human reader to reconstruct the original and contact the author: an email address such as, "no-one@example", becomes "no-one at example dot com", for instance.

Any e-mail address posted in public is likely to be automatically collected bycomputer softwareused by bulk emailers (a process known ase-mail address scavenging). Addresses posted onwebpages,Usenetorchat roomsare particularly vulnerable to this.Private e-mail sent between individuals is highly unlikely to be collected, but e-mail sent to amailing listthat isarchivedand made available via theweb,or passed onto aUsenetnews serverand made public, may eventually be scanned and collected.

Disadvantages

Disguising addresses makes it more difficult for people to sende-mailto each other. Many see it as an attempt to fix a symptom rather than solving the real problem ofe-mail spam,at the expense of causing problems for innocent users.In addition, there are e-mail address harvesters who have found ways to read the munged email addresses.

The use of address munging on Usenet is contrary to the recommendations of RFC 1036 governing the format of Usenet posts, which requires a valid e-mail address be supplied in the From: field of the post. In practice, few people follow this recommendation strictly.

Disguising e-mail addresses in a systematic manner (for example, user[at]domain[dot]com) offers little protection.

Any impediment reduces the user's willingness to take the extra trouble to email the user. In contrast, well-maintainede-mail filteringon the user's end does not drive away potential correspondents. No spam filter is 100% immune to false positives, however, and the same potential correspondent that would have been deterred by address munging may instead end up wasting time on long letters that will merely disappear into junk mail folders.

For commercial entities, maintaining contact forms on web pages rather than publicizing e-mail addresses may be one way to ensure that incoming messages are relatively spam-free yet do not get lost. In conjunction withCAPTCHAfields, spam on such comment fields can be reduced to effectively zero, except that non-accessibility of CAPTCHAs bring the same deterrent problems as address munging itself.

Alternatives

As an alternative to address munging, there are several "transparent" techniques that allow people to post a valid e-mail address, but still make it difficult for automated recognition and collection of the address:

• Content delivery networkvendors, such asCloudflare,offer email address obfuscation services to their clients.
• "Transparent name mangling" involves replacing characters in the address with equivalent HTML references from thelist of XML and HTML character entity references,e.g. the '@' gets replaced by either 'U+0040' or '@' and the '.' gets replaced by either 'U+002E' or '.' with the user knowing to take out the dashes.
• Posting all or part of the e-mail address as an image,for example, no-oneexample, where the at sign is disguised as an image, sometimes with thealternative textspecified as "@" to allow copy-and-paste, but while altering the address to remain outside of typicalregular expressionsof spambots.
• Using a client-side form with the e-mail address as a CSS3 animatedtext logocaptcha and shrinking it to normal size using inlineCSS.
• Posting an e-mail address with the order of characters jumbled and restoring the order using CSS.
• Building the link byclient-side scripting.
• Usingclient-side scriptingto produce a multi key email address encrypter.
• Usingserver-side scriptingto run a contact form.
• UsingBase64to encode the email address.

An example of munging "user@example" via client-side scripting would be:

<scripttype="text/javascript">
varname='user';
varat='@';
vardomain='example ';
document.write(name+at+domain);
</script>

The use of images and scripts for address obfuscation can cause problems for people usingscreen readersand users with disabilities, and ignores users of text browsers likelynxandw3m,although being transparent means they don't disadvantage non-English speakers that cannot understand the plain text bound to a single language that is part of non-transparent munged addresses or instructions that accompany them.

According to a 2003 study by theCenter for Democracy and Technology,even the simplest "transparent name mangling" of e-mail addresses can be effective.

Examples

Common methods of disguising addresses include:

Disguised address	Recovering the original address
no-one at example (dot) com	Replace "at" with "@", and "(dot)" with "."
[email protected]	Reversedomain name:elpmaxetoexample remove.invalid
moc.elpmaxe@eno-on	Reverse the entire address
no-one@exampleREMOVEME	Instructions in the address itself; remove REMOVEME
[email protected]	Remove NOSPAM and.invalidfrom the address.
n o - o n e @ e x a m p l e. c o m	This is still readable, but the spaces between letters stop most automatic spambots.
no-one<i>@</i>example<i>.</i>com (as HTML)	This is still readable and can be copied directly from webpages, but stops many email harvesters.
по-опе@ехатрlе.сот	Cannot be copied directly from Webpages, must be manually copied. All letters except l areCyrillichomoglyphsthat are identical to Latin equivalents to the human eye but are perceived differently by most computers. (See alsoIDN homograph attackfor more malicious use of this strategy.)
no-oneexample	Replace the image with "@".

The reservedtop-level domain.invalidis appended to ensure that a real e-mail address is not inadvertently generated.

See also

• Internet bot
• Netiquette