Electronic mail (e-mail) is a widely-used service. One needs to know an exact address for one's correspondent. Different forms of address may be feasible due to aliases for machine names which are supported at the correspondent's machine. However an unsupported form of address, or a mistyping of the address, will in most cases lead to a returned (``bounced'') message, and in some cases the failure to arrive at the intended destination will not be indicated to the sender. A number of suggestions are given in §7. if you wish to check up on someone's e-mail address. Use of any one of a range of mail programs (e.g. mail, xmh) is possible, which (still) most often support the transfer of plain text files only. To transfer binary data by e-mail, one should first use some appropriate ASCII coding of the binary data; examples include uuencode and uudecode.
In this article we employ both Internet and NSI-DECNet (formerly SPAN) address conventions. The DECNet form, NODE::NAME, can often be addressed using an Internet routing of the form name@node.dnet.nasa.gov. SPAN was closely related to VAX VMS systems, and is being overtaken by universal acceptance of the Internet. Note that the existence of a DECNet address does not necessarily imply that a corresponding Internet address also exists, although it is usually possible to route e-mail via gateway and forwarding systems. The NASA Science Internet Network Applications Information Center (NSI NAIC) provides a very useful guide for e-mail users (contact naic@nasa.gov).