strace of a smtpd/cleanup conversation:

    connect(10, {sa_family=AF_UNIX, path="public/cleanup"}, 110) = 0
    select(11, [10], NULL, [10], {3600, 0}) = 1 (in [10], left {3599, 960000})
    read(10, "queue_id\0CB60A405C\0\0", 4096) = 20

	cleanup first sends a queue id

    write(10, "flags\0002\0\0T\n1057620721S\nhjp@hjp.a"..., 216) = 216

	This really consists of two parts:
	    flags\0002\0\0
		is sent in the attr0 protocol described in util/attr_scan0.c

		The flags are described in global/cleanup_user.h:
		2 is "Enable content filter", 
		1 is "Bounce bad messages".

		We don't need 1 (we bounce the message ourselves), I'm not sure about
		2.

	    Starting at "T" is the protocol described on rec_type.h

    write(10, "N\rSubject: testN\0X\0E\0", 21) = 21

	here is the mail itself.

    read(10, "status\0000\0reason\0\0\0", 4096) = 18

	and cleanup responds with status 0 (ok).

	The cleanup states are also described in cleanup_user.h. 

	We need to translate them into proper SMTP relies(see smtpd/smtpd.c:data_cmd


another one (this time with longer strings:


    socket(PF_UNIX, SOCK_STREAM, 0)         = 10
    fcntl64(10, F_GETFL)                    = 0x2 (flags O_RDWR)
    fcntl64(10, F_SETFL, O_RDWR)            = 0
    connect(10, {sa_family=AF_UNIX, path="public/cleanup"}, 110) = 0
    select(11, [10], NULL, [10], {3600, 0}) = 1 (in [10], left {3599, 970000})
    read(10, "queue_id\0002491F405C\0\0", 4096) = 20

	wierd. The id contains leading zeros, but smtpd doesn't print them.
	And the length is different (11 bytes instead of 9).

    write(10, "flags\0002\0\0T\n1057621710S\nhjp@hjp.atR\17hjp@yoyo.hjp.atM\0N0Received: from localhost (localhost [127.0.0.1])N0\tby yoyo.hjp.at (Postfix) with SMTP id 2491F405CN>\tfor <hjp@yoyo.hjp.at>; Tue,  8 Jul 2003 01:48:30 +0200 (CEST)", 216) = 216

	envelope and header

    write(10, "N\rSubject: testN\0X\0E\0", 21) = 21

	the mail plus trailer

    read(10, "status\0000\0reason\0\0\0", 4096) = 18

	and cleanup's response.