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Chapter 34 |
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34. Options
Contents:
Command-Line Options
Configuration-File Options
Configuring with V8 m4 Options
Alphabetical Table of All Options
Option Argument Types
Interrelating Options
Pitfalls
Alphabetized Reference
Options affect the operation of the sendmail program. [1] Options can be specified in the command line, in the sendmail.cf file, and in a V8 m4 configuration. Among the many behavioral characteristics that can be tuned with options are the following examples:
[1] See Chapter 13, Setting Options , for a tutorial introduction to options.
-
Locations of all the other files that sendmail needs to access, such as the aliases file.
-
Location of the queue directory.
-
Time limits that should be applied to the Time To Live in the queue, the length of the wait with an SMTP connection, and so on.
-
Default permissions for files and the default user and group identities to use when not running as another user.
-
Degree of privacy desired, such as what kinds of inquiry to reject or who may examine the queue.
-
Modes of behavior, such as always queuing or running as a daemon and listening for incoming connections.
-
Limits that should be placed on system resources. Should one queue only under high load? Should one reserve minimal space in the queue?
-
Small bits of sendmail 's behavior, such as allowing colons to appear in addresses and stripping newlines from sender addresses.
Most options are preset in your sendmail.cf file to be appropriate for your site. Those that need local definitions will usually be indicated by comments. Some sites, especially those that have high mail loads or those connected to many different networks, will need to tune many of the options according to their unique needs.
34.1 Command-Line Options
Beginning with version 8.7 sendmail , command-line options may use multicharacter option names. Prior to version 8.7, only single characters were allowed. We describe the old form first, then the new.
34.1.1 Pre-V8.7 Command-Line Option Declarations
Prior to version 8.7, option names that are declared on the command line could be only a single character long:
-oXargumentprior to V8.7
The
-o
switch (lowercase
o
)
is immediately followed (with no intervening
space) by the one-letter name of the option (here,
X
). Depending
on the option selected, an
argument
may be required.
If that
argument
is present, it must immediately follow the
option name with no intervening space. Only one option may be specified
for each
-o
switch.
Under V8
sendmail
a space may appear between the
-o
and the
X
, but no space
may exist between the
X
and its
argument
.
This is because V8
sendmail
uses
getopt
(3) to parse its command line.
34.1.2 V8.7 Multicharacter Options in the Command Line
Beginning with version 8.7, option names
may be single-character or multicharacter.
Single-character options are declared with the
-o
(lower
case) switch as described above.
Multicharacter options are declared with a
-O
(uppercase) switch:
-OLongName=argumentuppercase
Space may optionally exist between the
-O
and the
LongName
. Space may not
exist between the
LongName
, the
=
, and the
argument
unless they are quoted:
-O "LongName = argument"
Only one option may be specified for each
-O
switch.
The sendmail program ignores case when it considers multicharacter names. Therefore the following three command lines have the same effect, and none produces an error:
-OQueueDirectory=/var/tmp -Oqueuedirectory=/var/tmp -OQuEuEdIrEcToRy=/var/tmp
34.1.2.1 Multicharacter name shorthand
Beginning with 8.7,
multicharacter names in the command line may
be specified by using the fewest unique
leftmost characters in the name.
For example, you can specify the queue directory
with the complete
QueueDirectory
long name:
%/usr/lib/sendmail -OQueueDirectory=/var/tmp
But if you need to run this command line frequently, [2] you may find it handy to use an abbreviation:
[2] With any of the modern utilities such as tcsh (1), ksh (1), or emacs (1), repetition may not require this shorthand.
%/usr/lib/sendmail -OQueueDir=/var/tmpOption QueueDir used as abbreviation for QueueDirectory
Whenever a multicharacter name is abbreviated, sendmail prints a warning (the second line above) to discourage you from using abbreviations inside your configuration file. It will also warn you if you specify too few leftmost letters:
%/usr/lib/sendmail -OQueue=/var/tmpreadcf: ambiguous option name Queue (matches QueueFactor and QueueDirectory)
If you misspell the single-character or multicharacter name, the following error is printed, and the option declaration is skipped:
%/usr/lib/sendmail -OQueDirectory=/var/tmpreadcf: unknown option name QueDirectory
Although these abbreviations can be handy on command lines, it is vital that you alway use nonabbreviated names in your configuration file. New options will be added to sendmail over time, and the use of abbreviations can lead to future unexpected or ambiguous effects.
34.1.3 Appropriateness of Options
Some options are intended for use only on the command line and make little or no sense when used in the configuration file. Options that are inappropriate in the configuration file are shown in Table 34.1 .
| Option Name | Description | ||
|---|---|---|---|
| ErrorMode |
(
e
) |
Section 34.8.24, ErrorMode (e) |
Set error mode. But note that in unusual circumstances it may be useful in a configuration file. |
| IgnoreDots |
(
i
) |
Section 34.8.32, IgnoreDots (i) |
Ignore dots. Use the |
(
M
) |
Section 34.8.77, (M) |
Define a macro. Use the D configuration command instead (see Section 31.3, "Configuration File Definitions" ). |
|
| MaxDaemonChildren | Section 34.8.35, MaxDaemonChildren |
Set maximum forked children. Although appropriate on the command-line when processing a queue, it should seldom be used in the configuration file. |
|
| SingleThreadDelivery | Section 34.8.64, SingleThreadDelivery |
Set single-threaded delivery. Although appropriate on the command-line when processing a queue, it should seldom be used in the configuration file. |
|
| Verbose |
(
v
) |
Section 34.8.76, Verbose |
Run in verbose mode. Use the |
34.1.4 Options that Are Safe
It is common practice to install sendmail so that it runs with root privilege. Security considerations normally require that sendmail give up that privilege for most command-line options specified by the ordinary user. But the ordinary user can specify a few options that allow sendmail to keep its root privilege. Those options are called "safe" and are shown in Table 34.2 .
| Option Name | Description | ||
|---|---|---|---|
| AllowBogusHELO | Section 34.8.3, AllowBogusHELO |
Allow no host with HELO or EHLO |
|
| CheckpointInterval |
(
C
) |
Section 34.8.7, CheckpointInterval (C) |
Checkpoint the queue |
| ColonOkInAddr | Section 34.8.9, ColonOkInAddr |
Allow colons in addresses |
|
| DefaultCharSet | Section 34.8.14, DefaultCharSet |
Define Content-Type: character set |
|
| DeliveryMode |
(
d
) |
Section 34.8.16, DeliveryMode (d) |
Set delivery mode |
| EightBitMode |
(
8
) |
Section 34.8.22, EightBitMode (8) |
How to convert MIME input |
| ErrorMode |
(
e
) |
Section 34.8.24 |
Specify mode for error handling |
| IgnoreDots |
(
i
) |
Section 34.8.32 |
Ignore leading dots in messages |
| LogLevel |
(
L
) |
Section 34.8.33, LogLevel (L) |
Set (increase) logging level a |
| MaxQueueRunSize | Section 34.8.38, MaxQueueRunSize |
Maximum queue messages processed |
|
| MeToo |
(
m
) |
Section 34.8.39, MeToo (m) |
Send to me too |
| MinFreeBlocks |
(
b
) |
Section 34.8.40, MinFreeBlocks (b) |
Define minimum free disk blocks |
| MinQueueAge | Section 34.8.41, MinQueueAge |
Skip queue file if too young |
|
| NoRecipientAction | Section 34.8.43, NoRecipientAction |
Handle no recipients in header |
|
| OldStyleHeaders |
(
o
) |
Section 34.8.44, OldStyleHeaders (o) |
Allow spaces in recipient lists |
| PrivacyOptions |
(
p
) |
Section 34.8.47, PrivacyOptions (p) |
Increase privacy of the daemon |
| QueueSortOrder | Section 34.8.51, QueueSortOrder |
How to pre-sort queue |
|
| SendMimeErrors |
(
j
) |
Section 34.8.60, SendMimeErrors (j) |
Return MIME format errors |
| SevenBitInput |
(
7
) |
Section 34.8.62, SevenBitInput (7) |
Force 7-bit input |
| SingleLineFromHeader | Section 34.8.63, SingleLineFromHeader |
Strip newlines from From: |
|
| SuperSafe |
(
s
) |
Section 34.8.67, SuperSafe (s) |
Queue everything just in case |
| UseErrorsTo |
(
l
) |
Section 34.8.74, UseErrorsTo (l) |
Use Errors-To: for errors |
| Verbose |
(
v
) |
Section 34.8.76 |
Run in verbose mode |
V8.7.3 was accidentally released with the
LogLevel
(
L
) option marked as not safe.
For example, the
AliasFile
(
A
) option
(location of the
aliases
file) is unsafe (and is not in
Table 34.2
).
If you were to send mail by specifying
a new location with the
AliasFile
option,
sendmail
would change
its identity from
root
to an ordinary user (you), thus
preventing
sendmail
from being able to queue its mail:
/var/spool/mqueue: Permission denied
Note that prior to V8.8.4, the
DontInitGroups
and
TryNullMXList
options were wrongly set to safe. This is yet another reason to always upgrade to the latest version of
sendmail
.
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| 33.8 Alphabetized Reference |
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34.2 Configuration-File Options |