Installation

Contents

• Compiling and Installing Your Filter
• Configuring Sendmail

Compiling and Installing Your Filter

• Put the include and Sendmail directories in your include path (e.g. -I/path/to/include -I/path/to/sendmail).
• Make sure libmilter.a is in your library path, and link your application with it (e.g. "-lmilter").
• Compile with pthreads, either by using -pthread for gcc, or linking with a pthreads support library (-lpthread).

cc -I/path/to/include -I/path/to/sendmail -c myfile.c

cc -o myfilter [object-files] -L[library-location] -lmilter -pthread

Configuring Sendmail

Next, you must add the desired filters to your sendmail configuration (.mc) file. Mail filters have three equates: The required S= equate specifies the socket where sendmail should look for the filter; the optional F= and T= equates specify flags and timeouts, respectively. All equates names, equate field names, and flag values are case sensitive.

The current flags (F=) are:

Flag	Meaning
R	Reject connection if filter unavailable
T	Temporary fail connection if filter unavailable

If a filter is unavailable or unresponsive and no flags have been specified, the MTA will continue normal handling of the current connection. The MTA will try to contact the filter again on each new connection.

There are four fields inside of the T= equate: C, S, R, and E. Note the separator between each is a ";" (semicolon), as "," (comma) already separates equates. The value of each field is a decimal number followed by a single letter designating the units ("s" for seconds, "m" for minutes). The fields have the following meanings:

Flag	Meaning
C	Timeout for connecting to a filter. If set to 0, the system's connect(2) timeout will be used. Default: 5m
S	Timeout for sending information from the MTA to a filter. Default: 10s
R	Timeout for reading reply from the filter. Default: 10s
E	Overall timeout between sending end-of-message to filter and waiting for the final acknowledgment. Default: 5m

The following sendmail.mc example specifies three filters. The first two rendezvous on Unix-domain sockets in the /var/run directory; the third uses an IP socket on port 999.

	INPUT_MAIL_FILTER(`filter1', `S=unix:/var/run/f1.sock, F=R')
	INPUT_MAIL_FILTER(`filter2', `S=unix:/var/run/f2.sock, F=T, T=S:1s;R:1s;E:5m')
	INPUT_MAIL_FILTER(`filter3', `S=inet:999@localhost, T=C:2m')

	define(`confINPUT_MAIL_FILTERS', `filter2,filter1,filter3')

	m4 ../m4/cf.m4 myconfig.mc > myconfig.cf

The above macros will result in the following lines being added to your .cf file:

        Xfilter1, S=unix:/var/run/f1.sock, F=R
        Xfilter2, S=unix:/var/run/f2.sock, F=T, T=S:1s;R:1s;E:5m
        Xfilter3, S=inet:999@localhost, T=C:2m

        O InputMailFilters=filter2,filter1,filter3

Finally, the sendmail macros accessible via smfi_getsymval can be configured by defining the following m4 variables (or cf options):

In .mc file	In .cf file	Default Value
confMILTER_MACROS_CONNECT	Milter.macros.connect	j, _, {daemon_name}, {if_name}, {if_addr}
confMILTER_MACROS_HELO	Milter.macros.helo	{tls_version}, {cipher}, {cipher_bits}, {cert_subject}, {cert_issuer}
confMILTER_MACROS_ENVFROM	Milter.macros.envfrom	i, {auth_type}, {auth_authen}, {auth_ssf}, {auth_author}, {mail_mailer}, {mail_host}, {mail_addr}
confMILTER_MACROS_ENVRCPT	Milter.macros.envrcpt	{rcpt_mailer}, {rcpt_host}, {rcpt_addr}

For information about available macros and their meanings, please consult the sendmail documentation.