1) Apply the patch.

2) Add the following to your Local/Makefile:
	SUPPORT_SRS=yes
	EXTRALIBS=-L<dir-containing-libsrs2> -lsrs2

3) Build.

4) Add the following global configuration variables to exim.conf.
All variables are optional, except where stated:
	srs_alwaysrewrite        (bool)
		If true, perform SRS rewriting for ALL forwarding,
		even when not required.
	srs_domain               (string)
		A domain to use in rewritten addresses. This must point only
		to machines which know the encoding secret used by this
		system. It defaults to [something sensible].
	srs_hashlength           (int)
		The hash length to generate in a rewritten address.
	srs_hashmin              (int)
		The hash length to require when checking an address.
	srs_maxage               (int)
		The maximum permitted age of a rewritten address.
	hide srs_secrets         (string)
		[required] A list of secrets with which to generate
		and check addresses.
	srs_separator            (string)
		The separator to appear immediately after SRS[01] in
		rewritten addresses.
See http://www.libsrs2.org/ for more information about the meaning
of these variables. They are standard across MTAs.

5) Add the following parameters to routers in exim.conf:
	forwarding_router:
		driver = redirect
		srs = forward
		data = ... [or file =, as usual]

	srs_router:
		driver = redirect
		srs = reverse
		data = ${srs_recipient}
		condition = ... [if desired]

6) Fire up and enjoy.