Programming Internet Email

Address Formats

Internet email addresses are of the form [e-mail]. There are many other forms of addressing for other types of network mail systems, such as DECnet, X.400, UUCP, etc. In this book, we will be concerned only with Internet-style addressing.

If you have a need to handle cross-network address translation, more information is available from !%@:: A Directory of Electronic Mail Addressing & Networks, by Donnalyn Frey and Rick Adams (O’Reilly Media, 1993), and in the chapter Rule Sets in sendmail, by Bryan Costales et. al. (O’Reilly Media, 1994).

Internet addresses may include comments. Any of the following are legitimate Internet mail address headers:

• To: [e-mail]

• CC: Chris Cruise <[e-mail]>

• BCC: “Spriesterbach, Ralph Q.” <[e-mail]>

• From: [e-mail] (The Big Guy)

• Apparently-To: Fred. (The Eliminator) [e-mail]

• Apparently-From: “A person with an Internet address mailed via an X.400 gateway” <IMCEAX400-c=au+3Ba=access400+3Bp=internet+3Bdda+3ARFC-822=[e-mail]>

The first and second addresses in the preceding list go to the same person. An MTA would parse them the same way to extract the valid address, [e-mail]. The first just gives the basic address, which is obviously valid. The second includes an unused (by the mail system) part, which gives a human-readable name as well. In order for a parser to identify the address itself, it is delimited with ...