Many people want to know what the F=T, T=C:10m;S:1s;R:1s; etc. in the milters means. 
Here is the explanation.


Per Sendmail:


+----------------------------------------+
| SPECIFYING FILTERS IN SENDMAIL CONFIGS |
+----------------------------------------+

Filters are specified with a key letter ``X'' (for ``eXternal'').

For example:

	Xfilter1, S=local:/var/run/f1.sock, F=R
	Xfilter2, S=inet6:999@localhost, F=T, T=C:10m;S:1s;R:1s;E:5m
	Xfilter3, S=inet:3333@localhost

specifies three filters.  Filters can be specified in your .mc file using
the following:

	INPUT_MAIL_FILTER(`filter1', `S=local:/var/run/f1.sock, F=R')
	INPUT_MAIL_FILTER(`filter2', `S=inet6:999@localhost, F=T, T=C:10m;S:1s;R:1s;E:5m')
	INPUT_MAIL_FILTER(`filter3', `S=inet:3333@localhost')

The first attaches to a Unix-domain socket in the /var/run directory; the
second uses an IPv6 socket on port 999 of localhost, and the third uses an
IPv4 socket on port 3333 of localhost.  The current flags (F=) are:

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

If neither F=R nor F=T is specified, the message is passed through sendmail
in case of filter errors as if the failing filters were not present.

Finally, you can override the default timeouts used by sendmail when
talking to the filters using the T= equate.  There are four fields inside
of the T= equate:

Letter		Meaning
  C		Timeout for connecting to a filter (if 0, use system timeout)
  S		Timeout for sending information from the MTA to a filter
  R		Timeout for reading reply from the filter
  E		Overall timeout between sending end-of-message to filter
		and waiting for the final acknowledgment

Note the separator between each is a ';' as a ',' already separates equates
and therefore can't separate timeouts.  The default values (if not set in
the config) are:

T=C:5m;S:10s;R:10s;E:5m

where 's' is seconds and 'm' is minutes.

Which filters are invoked and their sequencing is handled by the 
InputMailFilters option. Note: if InputMailFilters is not defined no filters
will be used.

	O InputMailFilters=filter1, filter2, filter3

This is is set automatically according to the order of the
INPUT_MAIL_FILTER commands in your .mc file.  Alternatively, you can
reset its value by setting confINPUT_MAIL_FILTERS in your .mc file.
This options causes the three filters to be called in the same order
they were specified.  It allows for possible future filtering on output
(although this is not intended for this release).

Also note that a filter can be defined without adding it to the input
filter list by using MAIL_FILTER() instead of INPUT_MAIL_FILTER() in your
.mc file.

To test sendmail with the sample filter, the following might be added (in
the appropriate locations) to your .mc file:

	INPUT_MAIL_FILTER(`sample', `S=local:/var/run/f1.sock')