Mail addresses identify both the originator and recipient of a mail
message. They generally take this form
X@Y
where X is a string, often a user or account, and Y
is a string, often a host. In this chapter, X represents the local part
of the mail address and Y represents the global part of the mail
address. Mail addresses appear in the To: and From: fields of the
message header and in the X-from: and X-to: fields of the envelope.
Envelope
The envelope is a header containing the originator and recipient
mail addresses. It is prepended to each mail message by the post office,
SNDMSG, or SSMTP, and it is used by all the Cisco IOS for S/390 SMTP
routines as the message travels through the system. The envelope
consists of the internally-defined (in other words, to the SMTP
routines) header fields, X-from: and X-to: that let the SMTP routines
convey mail addresses to one another.
Message Header
An RFC 822 message consists of any number of header fields,
optionally followed by message text. Typical header fields include:
Date:, From:, To:, CC: (carbon copy), and Subject:. The RFC 822
message header refers to the collection of these header fields.
Domain Literal
As defined in RFC 822, a domain literal is a dotted-decimal
host number enclosed in square brackets. This is an example of a mail
address using a domain literal: CZQ14CD@[10.10.0.1]
Multi-homed Host
Multi-homed hosts are connected to more than one network and
therefore have multiple network addresses.
Host Names
These are mnemonic name strings by which hosts are known on the
network. Each host has one official host name and can have optional
nicknames. Although nicknames are allowed, their use is discouraged as
discussed in RFC 952.
Domain Name Resolver
Cisco IOS for S/390 uses the Domain Name Resolver to map host names
into the appropriate network addresses.
Using the Mail Facilities
This section describes how to use the Cisco IOS for S/390 mail facilities for
the transportation of electronic mail.
Getting Started
Have your Cisco IOS for S/390 site administrator place an entry in the SMTP
User Table for you. This table defines a mapping between TSO user IDs and user
names. Each entry in the table contains these parameters:
TSO user ID
Mailbox name
A name by which the TSO user is known at other hosts on
your network. When SSMTP sends a message, it attempts to match the local
part of the recipient mail address against this field to map it into a TSO
user ID.
This optional parameter is used by USMTP in the
creation of an originating mail address (the X-From: header field in the
message header). For example, suppose the User Table had this entry:
USMTP transforms the header field (created by either
the post office or SNDMSG) from this format
