Using plain base32 ASCII-compatible encoding in the local part of E-mail addresses

The structure of Internet mails (or called E-mail) is specified in RFC 2822, which specifies message bodies as flat ASCII text. An E-mail address is in the form of local-part@domain. Internet Engineering Task Force (IETF) has set up a working group on internationalized domain names (IDN). A variety of proposals have been proposed for the format of ASCII-compatible encoding (ACE), which utilizes characters within the alphanumeric range [A-Z][0-9] and hyphen (-). Discussions on internationalization of the local part in E-mail addresses are also raised in the working group. We first address the lexical restrictions in E-mail addresses, system login names, and current E-mail systems. Secondly, we compare several design alternatives: base64, base62, base36, and base32. Thirdly, we address a plain base32 ACE for both IDN and local part of E-mail addresses.