Address munging is the practice of disguisingan e-mail address to prevent it from being automatically collected by unsolicited bulk e-mail providers.[1] 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.com", becomes "no-one at example dot com", for instance.
Any e-mail address posted in public is likely to be automatically collected by computer software used by bulk emailers (a process known as e-mail address scavenging). Addresses posted on webpages, Usenet or chat rooms are particularly vulnerable to this.[2] Private e-mail sent between individuals is highly unlikely to be collected, but e-mail sent to a mailing list that is archived and made available via the web, or passed onto a Usenet news server and made public, may eventually be scanned and collected.
Disguising addresses makes it more difficult for people to send e-mail to each other. Many see it as an attempt to fix a symptom rather than solving the real problem of e-mail spam, at the expense of causing problems for innocent users.[3] 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.[4]
Disguising e-mail addresses in a systematic manner (for example, user[at]domain[dot]com) offers little protection.[5]
Any impediment reduces the user's willingness to take the extra trouble to email the user. In contrast, well-maintained e-mail filtering on 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 with CAPTCHA fields, 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.
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:
An example of munging "user@example.com" via client-side scripting would be:
According to a 2003 study by the Center for Democracy and Technology, even the simplest "transparent name mangling" of e-mail addresses can be effective.[14] [15]
Common methods of disguising addresses include:
| Disguised address | Recovering the original address | |
|---|---|---|
| no-one at example (dot) com | Replace " at " with "@", and " (dot) " with "." | |
| no-one@elpmaxe.com.invalid | Reverse domain name: elpmaxe to example remove .invalid | |
| moc.elpmaxe@eno-on | Reverse the entire address | |
| no-one@exampleREMOVEME.com | Instructions in the address itself; remove REMOVEME | |
| no-one@exampleNOSPAM.com.invalid | Remove NOSPAM and .invalid from 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 are Cyrillic homoglyphs that are identical to Latin equivalents to the human eye but are perceived differently by most computers. (See also IDN homograph attack for more malicious use of this strategy.) | |
| no-oneexample.com | Replace the image with "@". |
The reserved top-level domain .invalid is appended to ensure that a real e-mail address is not inadvertently generated.