When porting
sendmail to a new system or tuning it for
special needs, you might need to adjust one of
sendmail's pre-defined
maximums. These cannot be tuned in your Build
m4 file. Instead, each needs to be changed in
the file indicated by the third column of Table 3-7. In general, maximums should never be changed
in either direction without first examining the code for possible
side effects. Check to see if any minimums are required or if any
warnings about maximums are evident in the code or in a README file.
Some of these limits are defined by RFC, and should not be changed
from the standard set by the appropriate RFC.
Table 3-7. Compile-time macros to redefine maximums
|
DEFAULT_MAX_RCPT
|
100
|
sendmail/conf.h
|
Initial max RCPTs per envelope (V8.12 and above)
|
|
ENHSCLEN
|
10
|
sendmail/conf.h
|
Length of enhanced status code
|
|
MACBUFSIZE
|
4096
|
sendmail/conf.h
|
Expansion of a defined macro
|
|
MAXALIASDB
|
12
|
sendmail/conf.h
|
Number of alias databases
|
|
MAXATOM
|
200
|
sendmail/conf.h
|
Atoms (tokens) in an address
|
|
MAXBADCOMMANDS
|
25
|
sendmail/srvrsmtp.c
|
Bad SMTP commands (V8.12 and above)
|
|
MAXDAEMONS
|
10
|
sendmail/conf.h
|
Ports on which to listen
|
|
MAXDNSRCH
|
6
|
sendmail/domain.c
|
Possible domains to search
|
|
MAXETRNCOMMANDS
|
8
|
sendmail/srvrsmtp.c
|
ETRNs before slowdown (V8.12 and above)
|
|
MAXFILTERMACROS
|
50
|
sendmail/conf.h
|
Macros per milter command (V8.12 and above)
|
|
MAXFILTERS
|
25
|
sendmail/conf.h
|
Milter filters (V8.12 and above)
|
|
MAXHDRSLEN
|
32768
|
sendmail/conf.h
|
Size of a message header
|
|
MAXHELOCOMMANDS
|
3
|
sendmail/srvrsmtp.c
|
HELO/EHLOs before slowdown (V8.12 and above)
|
|
MAXHOSTNAMELEN
|
256
|
sendmail/conf.h
|
Length of a hostname
|
|
MAXINTERFACES
|
512
|
sendmail/conf.h
|
Interfaces to probe at startup
|
|
MAXKEY
|
128
|
sendmail/conf.h
|
Length of a database key
|
|
MAXLINE
|
2048
|
sendmail/conf.h
|
Length of an input line
|
|
MAXLINKPATHLEN
|
131072
|
sendmail/conf.h
|
Symbolic link expansion
|
|
MAXMACNAMELEN
|
25
|
sendmail/conf.h
|
Length of a defined macro name
|
|
MAXMACROID
|
0377
|
sendmail/conf.h
|
Macro ID number (don't change)
|
|
MAXMAILERS
|
25
|
sendmail/conf.h
|
Number of delivery agents
|
|
MAXMAPSTACK
|
12
|
sendmail/conf.h
|
Size of sequenced map stack
|
|
MAXMIMEARGS
|
20
|
sendmail/conf.h
|
Arguments per Content-Type: header
|
|
MAXMIMENESTING
|
20
|
sendmail/conf.h
|
MIME multipart nesting
|
|
MAXMXHOSTS
|
100
|
sendmail/conf.h
|
Number of per-host MX records
|
|
MAXMIMENESTING
|
20
|
sendmail/conf.h
|
Multipart MIME nesting depth
|
|
MAXNAME
|
256
|
sendmail/conf.h
|
Length of a name
|
|
MAXNOOPCOMMANDS
|
20
|
sendmail/srvrsmtp.c
|
NOOPs, etc., before slowdown (V8.12 and above)
|
|
MAXPRIORITIES
|
25
|
sendmail/conf.h
|
Number of Priority lines
|
|
MAXPV
|
40
|
sendmail/conf.h
|
Arguments to a delivery agent
|
|
MAXQFNAME
|
20
|
sendmail/conf.h
|
qf filename length
|
|
MAXQUEUEGROUPS
|
50
|
sendmail/conf.h
|
Number of queue groups (V8.12 and above)
|
|
MAXRESTOTYPES
|
3
|
sendmail/conf.h
|
Number of resolver timeout types
|
|
MAXRULERECURSION
|
50
|
sendmail/conf.c
|
Rule set recursion
|
|
MAXRWSETS
|
200
|
sendmail/conf.h
|
Number of rule sets
|
|
MAXSHORTSTR
|
203
|
sendmail/conf.h
|
Length of a short string
|
|
MAXSYMLINKS
|
32
|
sendmail/conf.h
|
Number of symbolic links in a path
|
|
MAXTIMEOUT
|
(4 * 60)
|
sendmail/srvrsmtp.c
|
Timeout for slowdowns (V8.12 and above)
|
|
MAXTOCLASS
|
8
|
sendmail/conf.h
|
Message timeout classes
|
|
MAXUSERENVIRON
|
100
|
sendmail/conf.h
|
Environment items per delivery agent
|
|
MAXVRFYCOMMANDS
|
6
|
sendmail/srvrsmtp.c
|
VRFY/EXPNs before slowdown (V8.12 and above)
|
Also see QUEUESEGSIZE (QUEUESEGSIZE) and
SYSLOG_BUFSIZE (SYSLOG_BUFSIZE) for a discussion of two
other definitions that affect sizes.
Note that there are no debugging switches for displaying compiled
maximums. If you are running a binary distribution and a maximum is
of concern, you should get the source and build
sendmail yourself.
Beginning with V8.12, sendmail offers several
macros that slow down sendmail to prevent
certain types of attacks. They are listed in Table 3-8, which also shows their default settings.
Unlike the MAX... compile-time macros shown in
Table 3-7, these can be tuned as part of your
Build m4 file. For example,
to change the maximum number of NOOP SMTP commands that can be
received before sendmail slows itself down
defensively, you can add the following line to your
Build m4 file:
APPENDDEF(`conf_sendmail_ENVDEF', `-DMAXNOOPCOMMANDS=30 ')
increase from the default of 20
Table 3-8. Compile-Time Macros for Maximum Bad SMTP Commands
|
MAXBADCOMMANDS
|
25
|
Unrecognized SMTP commands
|
|
MAXETRNCOMMANDS
|
8
|
ETRN commands
|
|
MAXHELOCOMMANDS
|
3
|
HELO and EHLO commands
|
|
MAXNOOPCOMMANDS
|
20
|
NOOP commands
|
|
MAXTIMEOUT
|
(4 * 60)
|
Sleep time (seconds) after too many bad commands
|
|
MAXVRFYCOMMANDS
|
6
|
VRFY commands
|
If any of these SMTP-limiting compile-time macros are defined with a
zero value, the corresponding check is disabled. There is no
debugging command-line switch to display defaults with a precompiled
sendmail. If you need to change any of these
default settings, you must download and build
sendmail yourself.
