(registered 2014-03-26, last updated 2014-03-26) URI scheme name: smtp Status: provisional URI scheme syntax: smtpuri = "smtp://" authority ["/" [ "?" query ]] authority = query = If : is omitted from authority, the port defaults to 25. The query component is reserved for future extensions. URI scheme semantics: The smtp: URI scheme is used to designate SMTP servers (e.g. listener endpoints, S/MIME agents performing Domain signing), SMTP accounts. There is no MIME type associated with this URI. Encoding considerations: SMTP user names are UTF-8 strings and MUST be percent-encoded as required by the URI specification [RFC3986], Section 2.1. Applications/protocols that use this URI scheme name: The smtp: URI is intended to be used by applications that might need access to an SMTP server (for example email clients or MTAs) or for SMTP servers to describe their listener endpoints. Interoperability considerations: Several implementations are already using smtp: URIs for server configuration. Security considerations: Clients resolving smtp: URIs that wish to achieve data confidentiality and/or integrity SHOULD use the STARTTLS command (if supported by the server) before starting authentication, or use a SASL mechanism, such as GSSAPI, that provides a confidentiality security layer. Contact: Alexey Melnikov Author/Change controller: IESG References: [draft-melnikov-smime-msa-to-mda] and [RFC5321].