Source: https://docstore.mik.ua/orelly/networking/smdref/ch02_02.htm
Timestamp: 2019-04-24 11:51:32+00:00

Document:
In this section we list and describe each equate , where only the first letter of each is recognized (that is, Argv= is the same as A= ).
Lists the delivery agent's command-line arguments. The delivery agent speaks SMTP only if $u is absent from those arguments. The special symbolic argv0 names IPC and LPC reference internal sendmail code.
Uses the ISO-8859-1 character set in the MIME Content-Type: header (see §30.4.2). Applies to messages received from this delivery agent. Supersedes the DefaultCharSet option.
Sets the paths for execution of the prog delivery agent to /var/run first, and if it cannot chdir (2) into that directory, then to /tmp (see §30.4.3).
Specifies the end-of-line characters to be a carriage-return newline pair. Those characters are generated by sendmail for outgoing messages and recognized by sendmail for incoming messages. The default is \r\n for SMTP and \n otherwise (see §30.4.4).
Lists flags that describe a delivery agent's behavior (fully listed in the next section, "Delivery Agent F= Flags").
Limits the length of text lines in the body of a mail message to 512 characters (see §30.4.6).
Limits the total size (header and body combined) of messages handled by the delivery agent to one million characters.
Says to re- nice (2) the delivery agent by 5 (see §30.4.8).
Says to execute /usr/bin/uux as the delivery-agent program (see §30.4.9). Special symbolic paths can also be used: [ IPC ] makes a network connection and speaks SMTP; [ FILE ] appends the message to a file; and [ LPC ] is useful for tracking down mail problems.
Lists the rewriting rule set names or numbers for the recipient. A single name or number is applied to both envelope and header rewriting. Two names or numbers, separated by a slash, applies the leftmost to the envelope and the rightmost to headers (see §30.4.10).
Lists the rewriting rule set names or numbers for the sender. Particulars are the same as for R= above (see §30.4.11).
Sets the type tags used in the DSN diagnostic returns for this delivery agent. The type tag for the Reporting-MTA: field is DNS ; the type tag for the Final-Recipient: field is RFC822 ; and the type tag for the Diagnostic-Code: field is X-Unix (see §30.4.12).
Specifies that sendmail should become the user nullmail and the group nullgroup before executing the delivery agent. If the :nullgroup is omitted, it is found in the passwd (5) file entry for nullmail (see §30.4.13).

References: §30
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