The first rule simply replaces the
workspace with the value in the ${hdr_name} sendmail macro. That macro contains as
its current value the name of the header passed to this rule set.
The second rule checks, on its LHS, to see if the header name is one of those listed in
the class $={BannedRecipientHeaders}. If the header is found, the entire message is
rejected.
Note that this example will also reject inbound mail that contains Cc: or Bcc: headers.
A better design would include a test to be sure the message originated from the
local machine.
25.5.3 The check_eoh Rule Set
After all headers have been processed by sendmail, a couple of statistics become available
that can be of use in screening messages. One is the number of headers found. The
other is the total number of bytes in all the headers (including the names, colons,
whitespace, and values). If you should ever need this information, you can process it by
declaring a special rule set named check_eoh. If that rule set exists, it will be passed the
number of headers, and the total number of bytes in all the headers:
number of headers $| total bytes
This is the Title of the Book, eMatter Edition
Copyright ?© 2007 O??™Reilly & Associates, Inc. All rights reserved.
1136 | Chapter 25: The H (Headers) Configuration Command
If it exists, sendmail will call the check_eoh rule set after all headers have otherwise
been processed.
Pages:
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048