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早期freebsd实现

		try to divine: the name of your kernel, the name of the
		variable in the kernel to examine, the number of bits of
		precision in a fixed point load average, and so forth.
		In desperation, use LA_ZERO.  The actual code is in
		conf.c -- it can be tweaked if you are brave.
SFS_TYPE	Encodes how your kernel can locate the amount of free
		space on a disk partition.  This can be set to SFS_NONE
		(0) if you have no way of getting this information,
		SFS_USTAT (1) if you have the ustat(2) system call,
		SFS_4ARGS (2) if you have a four-argument statfs(2)
		system call (and the include file is <sys/statfs.h>),
		and SFS_VFS (3), SFS_MOUNT (4), SFS_STATFS (5) or
		SFS_STATVFS (6) if you have the two-argument statfs(2)
		system call, with includes in <sys/vfs.h>, <sys/mount.h>,
		<sys/statfs.h>, or <sys/statvfs.h> respectively.  The
		default if nothing is defined is SFS_NONE.
ERRLIST_PREDEFINED
		If set, assumes that some header file defines sys_errlist.
		This may be needed if you get type conflicts on this
		variable -- otherwise don't worry about it.
WAITUNION	The wait(2) routine takes a "union wait" argument instead
		of an integer argument.  This is for compatibility with
		old versions of BSD.
SCANF		You can set this to extend the F command to accept a
		scanf string -- this gives you a primitive parser for
		class definitions -- BUT it can make you vulnerable to
		core dumps if the target file is poorly formed.
SYSLOG_BUFSIZE	You can define this to be the size of the buffer that
		syslog accepts.  If it is not defined, it assumes a
		1024-byte buffer.  If the buffer is very small (under
		256 bytes) the log message format changes -- each
		e-mail message will log many more messages, since it
		will log each piece of information as a separate line
		in syslog.
BROKEN_RES_SEARCH
		On Ultrix (and maybe other systems?) if you use the
		res_search routine with an unknown host name, it returns
		-1 but sets h_errno to 0 instead of HOST_NOT_FOUND.  If
		you set this, sendmail considers 0 to be the same as
		HOST_NOT_FOUND.


+-----------------------+
| COMPILE-TIME FEATURES |
+-----------------------+

There are a bunch of features that you can decide to compile in, such
as selecting various database packages and special protocol support.
Several are assumed based on other compilation flags -- if you want to
"un-assume" something, you probably need to edit conf.h.  Compilation
flags that add support for special features include:

NDBM		Include support for "new" DBM library for aliases and maps.
		Normally defined in the Makefile.
NEWDB		Include support for Berkeley "db" package (hash & btree)
		for aliases and maps.  Normally defined in the Makefile.
OLD_NEWDB	If non-zero, the version of NEWDB you have is the old
		one that does not include the "fd" call.  This call was
		added in version 1.5 of the Berkeley DB code.  If you
		use -DOLD_NEWDB=0 it forces you to use the new interface.
NIS		Define this to get NIS (YP) support for aliases and maps.
		Normally defined in the Makefile.
USERDB		Include support for the User Information Database.  Implied
		by NEWDB in conf.h.
IDENTPROTO	Define this as 1 to get IDENT (RFC 1413) protocol support.
		This is assumed unless you are running on Ultrix or
		HP-UX, both of which have a problem in the UDP
		implementation.  You can define it to be 0 to explicitly
		turn off IDENT protocol support.
MIME		Include support for MIME-encapsulated error messages.
LOG		Set this to get syslog(3) support.  Defined by default
		in conf.h.  You want this if at all possible.
NETINET		Set this to get TCP/IP support.  Defined by default
		in conf.h.  You probably want this.
NETISO		Define this to get ISO networking support.
SMTP		Define this to get the SMTP code.  Implied by NETINET
		or NETISO.
NAMED_BIND	Define this to get DNS (name daemon) support, including
		MX support.  The specs you must use this if you run
		SMTP.  Defined by default in conf.h.
QUEUE		Define this to get queueing code.  Implied by NETINET
		or NETISO; required by SMTP.  This gives you other good
		stuff -- it should be on.
DAEMON		Define this to get general network support.  Implied by
		NETINET or NETISO.  Defined by default in conf.h.  You
		almost certainly want it on.
MATCHGECOS	Permit fuzzy matching of user names against the full
		name (GECOS) field in the /etc/passwd file.  This should
		probably be on, since you can disable it from the config
		file if you want to.  Defined by default in conf.h.
SETPROCTITLE	Try to set the string printed by "ps" to something
		informative about what sendmail is doing.  Defined by
		default in conf.h.


+---------------------+
| DNS/RESOLVER ISSUES |
+---------------------+

Many systems have old versions of the resolver library.  At a minimum,
you should be running BIND 4.8.3; older versions may compile, but they
have known bugs that should give you pause.

Common problems in old versions include "undefined" errors for
dn_skipname.

Some people have had a problem with BIND 4.9; it uses some routines
that it expects to be externally defined such as strerror().  It may
help to link with "-l44bsd" to solve this problem.

!PLEASE! be sure to link with the same version of the resolver as
the header files you used -- some people have used the 4.9 headers
and linked with BIND 4.8 or vice versa, and it doesn't work.
Unfortunately, it doesn't fail in an obvious way -- things just
subtly don't work.


+-------------------------------------+
| OPERATING SYSTEM AND COMPILE QUIRKS |
+-------------------------------------+

GCC 2.5.x problems  *** IMPORTANT ***
	Date: Mon, 29 Nov 93 19:08:44 PST
	From: [e-mail] (Jim Wilson)
	Message-Id: <[e-mail]>
	To: [e-mail]
	Subject: [[e-mail]: gcc 2.5.4-2.5.5 -O bug]
	Cc: [e-mail], [e-mail], [e-mail]

	This fixes a problem that occurs when gcc 2.5.5 is used to compile
	sendmail 8.6.4 with optimization on a sparc.

	Mon Nov 29 19:00:14 1993  Jim Wilson  ([e-mail])

		* reload.c (find_reloads_toplev): Replace obsolete reference to
		BYTE_LOADS_*_EXTEND with LOAD_EXTEND_OP.

	*** clean-ss-931128/reload.c    Sun Nov 14 16:20:01 1993
	--- ss-931128/reload.c  Mon Nov 29 18:52:55 1993
	*************** find_reloads_toplev (x, opnum, type, ind
	*** 3888,3894 ****
		 force a reload in that case.  So we should not do anything here.  */
	  
		else if (regno >= FIRST_PSEUDO_REGISTER
	! #if defined(BYTE_LOADS_ZERO_EXTEND) || defined(BYTE_LOADS_SIGN_EXTEND)
		       && (GET_MODE_SIZE (GET_MODE (x))
			   <= GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
	  #endif
	--- 3888,3894 ----
		 force a reload in that case.  So we should not do anything here.  */
	  
		else if (regno >= FIRST_PSEUDO_REGISTER
	! #ifdef LOAD_EXTEND_OP
		       && (GET_MODE_SIZE (GET_MODE (x))
			   <= GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
	  #endif


SunOS 4.x (Solaris 1.x)
	You may have to use -lresolv on SunOS.  However, beware that
	this links in a new version of gethostbyname that does not
	understand NIS, so you must have all of your hosts in DNS.

	Some people have reported problems with the SunOS version of
	-lresolv and/or in.named, and suggest that you get a newer
	version.  The symptoms are delays when you connect to the
	SMTP server on a SunOS machine or having your domain added to
	addresses inappropriately.  There is a version of BIND
	version 4.9 on gatekeeper.DEC.COM in pub/BSD/bind/4.9.

	There is substantial disagreement about whether you can make
	this work with resolv+, which allows you to specify a search-path
	of services.  Some people report that it works fine, others
	claim it doesn't work at all (including causing sendmail to
	drop core when it tries to do multiple resolv+ lookups for a
	single job).  I haven't tried resolv+, as we use DNS exclusively.

	Should you want to try resolv+, it is on ftp.uu.net in
	/networking/ip/dns.

Solaris 2.x (SunOS 5.x)
	To compile for Solaris, be sure you use -DSOLARIS.

	To the best of my knowledge, Solaris does not have the
	gethostbyname problem described above.  However, it does
	have another one:

	From a correspondent:

	   For solaris 2.2, I have 

		hosts:      files dns

	   in /etc/nsswitch.conf and /etc/hosts has to have the fully
	   qualified host name. I think "files" has to be before "dns"
	   in /etc/nsswitch.conf during bootup.

	From another correspondent:

	   When running sendmail under Solaris, the gethostbyname()
	   hack in conf.c which should perform proper canonicalization
	   of host names could fail.  Result: the host name is not
	   canonicalized despite the hack, and you'll have to define $j
	   and $m in sendmail.cf somewhere.

	   The reason could be that /etc/nsswitch.conf is improperly
	   configured (at least from sendmail's point of view).  For
	   example, the line

		hosts:      files nisplus dns

	   will make gethostbyname() look in /etc/hosts first, then ask
	   nisplus, then dns.  However, if /etc/hosts does not contain
	   the full canonicalized hostname, then no amount of
	   gethostbyname()s will work.

	   Solution (or rather, a workaround): Ask nisplus first, then
	   dns, then local files:

		hosts:      nisplus dns [NOTFOUND=return] files

	The Solaris "syslog" function is apparently limited to something
	about 90 characters because of a kernel limitation.  If you have
	source code, you can probably up this number.  You can get patches
	that fix this problem: the patch ids are:

		Solaris 2.1	100834
		Solaris 2.2	100999
		Solaris 2.3	101318

	Be sure you have the appropriate patch installed or you won't
	see system logging.

OSF/1
	If you are compiling on OSF/1 (DEC Alpha), you must use 
	-L/usr/shlib (otherwise it core dumps on startup).  You may also
	need -mld to get the nlist() function, although some versions
	apparently don't need this.
	
	Also, the enclosed makefile removed /usr/sbin/smtpd; if you need
	it, just create the link to the sendmail binary.

IRIX
	The header files on SGI IRIX are completely prototyped, and as
	a result you can sometimes get some warning messages during
	compilation.  These can be ignored.  There are two errors in
	deliver only if you are using gcc, both of the form ``warning:
	passing arg N of `execve' from incompatible pointer type''.
	Also, if you compile with -DNIS, you will get a complaint
	about a declaration of struct dom_binding in a prototype
	when compiling map.c; this is not important because the
	function being prototyped is not used in that file.

NeXT
	If you are compiling on NeXT, you will have to create an empty
	file "unistd.h" and create a file "dirent.h" containing:

		#include <sys/dir.h>
		#define dirent	direct

	(The Makefile.NeXT should try to do both of these for you.)

	Apparently, there is a bug in getservbyname on Nextstep 3.0
	that causes it to fail under some circumstances with the
	message "SYSERR: service "smtp" unknown" logged.  You should
	be able to work around this by including the line:

		OOPort=25

	in your .cf file.

	You may have to use -DNeXT.

BSDI (BSD/386) 1.0, NetBSD 0.9, FreeBSD 1.0
	The "m4" from BSDI won't handle the config files properly.
	I haven't had a chance to test this myself.

	The M4 shipped in FreeBSD and NetBSD 0.9 don't handle the config
	files properly. One must use either GNU m4 1.1 or the PD-M4
	recently posted in comp.os.386bsd.bugs (and maybe others).
	NetBSD-current includes the PD-M4 (as stated in the NetBSD file
	CHANGES).
	
	FreeBSD 1.0 RELEASE has uname(2) now. Use -DUSEUNAME in order to
	use it (look into Makefile.FreeBSD). NetBSD-current may have
	it too but it has not been verified.

	You cannot port the latest version of the Berkeley db library
	and use it with sendmail without recompiling the world.  This
	is because C library routines use the older version which have
	incompatible header files -- the result is that it can't read