RFC 6068 Mailto Specification & Limitations
Understanding the Internet Engineering Task Force (IETF) standards, valid query parameters, and security models of mailto URIs.
What is RFC 6068?
Published in October 2010 (obsoleting the older RFC 2368 from 1998), RFC 6068 defines the Internet URI scheme for mailto.
Its main purpose is to designate the Internet mailing address of an individual or service. It specifies standard header fields that can be populated to allow simple message composition.
Valid Query Parameters
RFC 6068 defines standard query parameters for mailto links, such as to, cc, bcc, subject, and body. In general web environments, unrecognized query keys are ignored by resolving email applications.
Core Standard Behavior:
RFC 6068 does not define any attachment mechanism. Unrecognized parameters are not part of the standard protocol and cannot be reliably supported by email clients.
Specification Boundaries
Because RFC 6068 does not define any attachment parameters, custom query elements such as ?attachment= fall outside the internet standards. Standard web browsers and email clients enforce security boundaries that prevent remote web pages from commanding local email software to access local files. Consequently, unrecognized fields are ignored by compliant clients.
Building Standard-Compliant Mailto Links
Need to generate clean, standard-compliant mailto links? Use our free tool or check alternatives to direct attachments.