.invalid
Encyclopedia : I : IN : INV : .invalid
.invalid is a reserved top-level domain not intended for real use in the global DNS. It was defined in June 1999 by RFC 2606, along with .test, .localhost, and .example.
.invalid was created to provide TLD's for use in places where a user wishes to enter an address that is known not to work. Using .invalid at the end of munged e-mail addresses is strongly recommended in order to minimise the load placed on legitimate systems if the address is harvested by spammers. If the munged address contains a valid domain (and many obvious possibilities like example.com are in fact valid) then bulk mail to non-existent sub-domains and users must be routed and then rejected by the servers at that site. If the munged domain is not valid, then a certain amount of DNS activity is still required to determine that fact, whereas in both cases a lookup for a .invalid address can be rejected at the first opportunity.
Some consider the use of an invalid address in a "From" field (for instance, in newsgroup postings) to be a standards violation, whether or not it is properly marked using the .invalid TLD; a possible interpretation of the relevant RFC documents holds that such fields must always have valid addresses at which the author of the message is reachable.
| Generic top-level domains | ||
|---|---|---|
| Unsponsored | .biz .com .edu .gov .info .int .mil .name .net .org | |
| Sponsored | .aero .cat .coop .jobs .museum .pro .travel | |
| Infrastructure | .arpa .root | |
| Startup phase | .mobi .post .tel | |
| Proposed | .asia .geo .kid .kids .mail .sco .web .xxx | |
| Deleted/retired | .nato | |
| Reserved | .example .invalid .localhost .test | |
| Pseudo-domains | .bitnet .csnet .local .onion .uucp | |
| Unofficial | see Alternative DNS roots | |
| See also: Country code top-level domains | ||
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