sendmail, 4th Edition

C=

Default MIME character set V8.7 and later

The C= delivery agent equate (introduced with V8.7 sendmail) is used to define a default character set for use with the MIME Content-Type: header (Content-Type: on page 1154). If it is present, its value supersedes that of the DefaultCharSet option (DefaultCharSet on page 1000).

Note that the C= delivery agent equate is examined only when the delivery agent is selected for an envelope sender address.

When a mail message is converted from 8 to 7 bits (see the EightBitMode option in EightBitMode on page 1025) it is important that the result looks like a MIME message. V8.7 sendmail first outputs the following header (if one is not already present):

MIME-Version: 1.0

Next, V8.7 sendmail looks for a Content-Type: header (Content-Type: on page 1154). If none is found, the following is inserted, where charset is the value declared for the C= delivery agent equate of the sender’s delivery agent:

Content-Type: text/plain; charset=charset

If the argument to C= is missing, the following error is printed and C= becomes undefined:

mailer agent_name: null charset

If the C= delivery agent equate is undefined in your configuration file, charset defaults to the value of the DefaultCharSet option. If both are undefined, the value for charset becomes unknown-8bit.