Options determine most of the sendmail program's behavior. They are declared on the command line with the -O switch:
and in the configuration file with the O line:
The space following the O is mandatory. Prior to V8.7 sendmail, option names could be only a single character. Beginning with V8.7, option names can be multi-character. Where appropriate, the old form is listed parenthetically after the new form.
True/False options, when absent, default to false, but when present with no value, default to true. Options marked as "(safe)" can be specified on the command line without giving up root privileges.
Defines the location (and optionally the type
as type:file) of the aliases file or files.
(Was the A option, see §34.8.1,
ALIAS_FILE with the m4 technique.)
Specifies the interval sendmail will wait for
the aliases database to rebuild.
(Was the a option, see §34.8.2,
confALIAS_WAIT with the m4 technique.)
(safe) allows sendmail to accept an SMTP HELO or EHLO that is not followed by a hostname (see §34.8.3).
Allows sendmail to automatically rebuild the aliases database.
(Was the D option, see §34.8.4,
confAUTO_REBUILD with the m4 technique.)
Specifies the unquoted space replacement character char.
(Was the B option, see §34.8.5,
confBLANK_SUB with the m4 technique.)
(safe) tells sendmail to check the right side of aliases
in the aliases file in addition to the normal
left side checks.
(Was the n option, see §34.8.6,
confCHECK_ALIASES with the m4 technique.)
(safe) states the number of recipients that will be delivered
between checkpoints (flushes to disk) of the qf file.
(Was the C option, see §34.8.7,
confCHECKPOINT_INTERVAL with the m4 technique.)
Sets the multiplication factor for calculating
(Was the z option, see §34.8.8,
confWORK_CLASS_FACTOR with the m4 technique.)
(safe) tells sendmail to allow colons in addresses,
thus disabling recognition of
:; list addresses - DECnet
:: is always allowed
confCOLON_OK_IN_ADDR with the m4 technique).
Stipulates the number of simultaneous open SMTP connections
sendmail will maintain during delivery.
(Was the k option, see §34.8.10,
confMCI_CACHE_SIZE with the m4 technique.)
Stipulates the duration of time any given open, but when idle,
SMTP connection will be maintained.
(Was the K option, see §34.8.11,
confMCI_CACHE_ TIMEOUT with the m4 technique.)
Specifies the maximum number of incoming connections
that will be accepted per second. Additional connections
are accepted progressively more slowly
confCONNECTION_ RATE_THROTTLE with the m4 technique).
Sets the daemon TCP/IP port options.
Available options are:
Addr is the network to accept connections from;
Family is the type of network;
Listen is the size of the listen(2) queue;
Port is the port on which sendmail should listen;
ReceiveSize is the size of the TCP/IP receive buffer;
SendSize is the size of the TCP/IP send buffer.
(Was the O option, see §34.8.13,
confDAEMON_ OPTIONS with the m4 technique.)
(safe) Defines the character set that will be
listed in the
header, for MIME 8- to 7-bit conversion
confDEF_CHAR_ SET with the m4 technique).
Specifies the default non-root identity for sendmail.
The user may be a numeric uid or a login name.
If group is omitted, user is looked up in
the passwd(5) database, and that gid is used.
Otherwise, group may be a numeric gid or a group name.
(Was the u and g options, see §34.8.15,
confDEF_ USER_ID with the m4 technique.)
(safe) sets the delivery mode that sendmail will run as.
Select mode from:
background to run asynchronously;
interactive to run synchronously;
queue-only to queue, rather than deliver, all mail;
deferred to queue all mail without doing
any DNS lookups.
(Was the d option, see §34.8.16,
confDELIVERY_MODE with the m4 technique.)
(safe) specifies how long to sleep after a connection failure.
If non-zero, sleeps that interval then tries again
confDIAL_DELAY with the m4 technique).
Prevents CNAME expansion when looking up
confDONT_ EXPAND_CNAMES with the m4 technique).
Suppresses use of the initgroups(3) call to
look up additional group memberships
confDONT_INIT_GROUPS with the m4 technique).
Prevents sendmail from short-circuiting source routes.
(Was the R option, see §34.8.20,
confDONT_PRUNE_ROUTES with the m4 technique.)
Specifies the address to which an error message should be sent
if there is an error sending an error message
confDOUBLE_BOUNCE_ADDRESS with the m4 technique).
(safe) specifies how to convert unlabeled MIME input.
mimify to force conversion of 8BITMIME to 7-bit;
pass to pass unlabeled 8-bit input through as-is;
strict to reject unlabeled 8-bit input.
(Was the 8 option, see §34.8.22,
confEIGHT_BIT_HANDLING with the m4 technique.)
(safe) specifies text or a file's contents to insert at
the top of bounced messages.
If the description starts with a slash, it is
taken as the full pathname of a file, otherwise
the description is taken as literal text.
The text is macro-expanded during interpolation.
(Was the E option, see §34.8.23,
confERROR_MESSAGE with the m4 technique.)
(safe) specify mode of error handling.
m to mail error notification to the sender no matter what;
e to act just like
m, but to always exit with a zero exit status;
p to print error messages (the default);
q to remain silent about all delivery errors;
w to write errors to the sender's terminal screen.
(Was the e option, see §34.8.24,
confERROR_ MODE with the m4 technique.)
Specifies the host to send mail to when all connections to
the actual MX hosts have failed.
(Was the V option, see §34.8.25,
confFALLBACK_MX with the m4 technique.)
Causes queue files to be processed individually to
lessen the impact on small-memory machines.
(Was the Y option, see §34.8.26,
confSEPARATE_PROC with the m4 technique.)
Sets the ~/.forward search path.
Each file name is macro-expanded, then tried.
Each is tried in turn until one can be read, whereupon
it is the ~/.forward for that local recipient.
(Was the J option, see §34.8.27,
confFORWARD_PATH with the m4 technique.)
Specifies the location of the file that
contains help messages for the SMTP (and ESMTP)
HELP command, and usage for the -bt rule-testing
(Was the H option, see §34.8.28,
HELP_FILE with the m4 technique.)
Tells sendmail to queue rather than deliver messages
that will be delivered by "expensive" delivery agents (those
with an F=e flag set).
(Was the c option, see §34.8.29,
confCON_ EXPENSIVE with the m4 technique.)
Specifies an alternative for the /etc/hosts file
(see §34.8.30, or define
confHOSTS_FILE with the m4 technique).
Specifies the directory in which sendmail should
store persistent host status. If specified, this also
enables the keeping of that status. A relative name is
relative to the queue directory
confHOST_STATUS_DIRECTORY with the m4 technique).
(safe) tells sendmail to ignore leading dots in the message body.
(Was the i option, see §34.8.32,
confIGNORE_DOTS with the m4 technique.)
(safe) sets the logging level, where a level of:
0-6 logs progressively less serious problems;
7 logs delivery failures;
8 logs delivery successes;
9 logs deferred delivery;
10-11 logs database and nis lookups;
12 logs SMTP connects;
13 logs questionable permissions;
14 logs connection refusals;
15 logs all incoming and outgoing SMTP commands;
16-98 logs progressively more detailed debugging
On the command line, you can only increase the logging level.
(Was the L option, see §34.8.33,
confLOG_LEVEL with the m4 technique.)
Enables so called "Fuzzy"
matching of the recipient in the gecos field
of the passwd(5) database.
(Was the G option, see §34.8.34,
confMATCH_ GECOS with the m4 technique.)
Specifies maximum number of children that sendmail will
fork to process inbound connections. Does not limit forked
children that process the queue
confMAX_DAEMON_CHILDREN with the m4 technique).
Sets the maximum number of times a message may be relayed
through mail-handling sites (the maximum hop count).
(Was the h option, see §34.8.36,
confMAX_HOP with the m4 technique.)
Specifies the maximum size (in bytes) of an incoming
message that sendmail will accept
confMAX_MESSAGE_SIZE with the m4 technique).
(safe) specifies the maximum number of queued messages that sendmail
will process from a queue in a given queue run
confMAX_QUEUE_RUN_SIZE with the m4 technique).
(safe) causes a copy of the message to be sent to the sender too, when
the sender is one of the recipients listed in an alias or
(Was the m option, see §34.8.39,
confME_TOO with the m4 technique.)
(safe) defines minimum number of free disk blocks that
must be available when a message's size is stated
with the SIZE keyword to the ESMTP MAIL
(Was the b option, see §34.8.40,
confMIN_FREE_BLOCKS with the m4 technique.)
(safe) skips processing of a queued file if the last time
it was processed is sooner than the interval specified
confMIN_ QUEUE_AGE with the m4 technique).
Allows sendmail to quote nonaddress characters in an address, as required by RFC822 (see §34.8.42).
(safe) specifies how to handle the situation of no recipients being
specified in the header (as would be the case when all recipients
were specified in
add-apparently-to, which adds an
add-bcc, which adds an empty
add-to, which adds an empty
add-undisclosed, which adds a
none, which passes the message unchanged
confNO_RCPT_ACTION with the m4 technique).
(safe) causes sendmail to insert commas between the recipients
listed in a space-delimited list of recipients.
(Was the o option, see §34.8.44,
confOLD_STYLE_HEADERS with the m4 technique.)
Sets token-separation operators to the list of characters
(Was the $o macro, see §34.8.45,
confOPERATORS with the m4 technique.)
Enables the user, whose email address is given, to receive
an extra copy of every bounce message.
(Was the P option, see §34.8.46,
confCOPY_ERRORS_TO with the m4 technique.)
(safe) increases privacy and security of the daemon.
Each option adds to earlier options. Select from:
authwarnings, which enables
needexpnhelo, which requires SMTP HELO before EXPN;
needmailhelo, which requires SMTP HELO before MAIL;
needvrfyhelo, which requires SMTP HELO before VRFY;
noexpn, which disables all SMTP EXPN commands;
novrfy, which disables all SMTP VRFY commands;
goaway, which enables all the preceding.
Also select from:
public, which means none of the preceding;
restrictmailq, which restricts who may run mailq(1);
restrictqrun, which restricts who may process the queue;
noreceipts, which disables sending of return-receipt mail.
(Was the p option, see §34.8.47,
confPRIVACY_ FLAGS with the m4 technique.)
Specifies the full pathname of the queue directory.
(Was the Q option, see §34.8.48,
QUEUE_DIR with the m4 technique.)
Sets the factor for high-load queuing. When a message is received, the decision to deliver or to queue it is based on the formula:
priority > QueueFactor / (load - QueueLA + 1)
If the priority of the message is greater than the result of this
load is the current load average, the message
is delivered. (Was the q option, see §34.8.49,
confQUEUE_FACTOR with the m4 technique.)
Specifies the load average above which queue runs will be skipped.
This is also used in the formula shown above for QueueFactor.
(Was the x option, see §34.8.50,
confQUEUE_LA with the m4 technique.)
(safe) specifies how to presort the queue.
host to sort by recipient host, lock status, and priority;
priority for a simple sort of the message priorities;
time to sort based on submission time
confQUEUE_ SORT_ORDER with the m4 technique).
Limits the life of a queued message to the interval specified.
The first delivery failure after that interval is exceeded
causes the message to bounce. (Was the T option; deprecated,
Timeout.queuereturn option instead.)
Penalizes large recipient lists by multiplying the number of
recipients by this factor when determining a message's priority.
(Was the y option, see §34.8.53,
confWORK_RECIPIENT_FACTOR with the m4 technique.)
Tells sendmail to refuse incoming SMTP connections
when the load average exceeds this specified load.
(Was the X option, see §34.8.54,
or define %
confREFUSE_LA with the m4 technique.)
Tunes DNS lookups by specifying an arg, or args, such as:
+AAONLY, which turns on the AAONLY name server option
(Authoritative Answers Only);
-DNSRCH, which turns off the DNSRCH
name server option (search the domain path).
(Was the I option, see §34.8.55,
confBIND_OPTS with the m4 technique.)
Sets the amount to increment a job's priority each time
a message fails to be delivered.
(Was the Z option, see §34.8.56,
confWORK_ TIME_FACTOR with the m4 technique.)
Runs sendmail as a user other than root.
The user may be a numeric uid or a login name.
If group is omitted, user is looked up in
the passwd(5) database and the primary gid is used.
Otherwise, group may be a numeric gid or a group name
confRUN_AS_USER with the m4 technique).
Sets the pathname to a directory that is safe for file writes. The
sendmail program does a chroot(2) to that
directory before writing to files.
Also prevents writing to other than plain files,
with the exception of /dev/null
confSAFE_ FILE_ENV with the m4 technique).
Prevents sendmail from removing
UNIX mailbox-style From lines from input.
(Was the f option, see §34.8.59,
confSAVE_FROM_LINES with the m4 technique.)
(safe) Tells sendmail it may return error messages (bounced mail
notifications) in MIME format.
(Was the j option, see §34.8.60,
confMIME_ FORMAT_ERRORS with the m4 technique.)
Specifies the location of the switched-services file.
Under Solaris, DEC OSF/1, and Ultrix, this
option is ignored, and the system file automatically used.
A switch-services file defines how and in what order
services, such as alias, host, and user information,
will be looked up
confSERVICE_SWITCH_FILE with the m4 technique).
(safe) Forces sendmail to clear the high-bit of each byte of a message's
body that it reads.
(Was the 7 option, see §34.8.62,
confSEVEN_ BIT_INPUT with the m4 technique.)
(safe) Tells sendmail to strip all newline characters
Ensures that only a single sendmail
will ever be delivering to a given host at a given time.
Requires that the
HostStatusDirectory option be set
confSINGLE_THREAD_ DELIVERY with the m4 technique).
Specifies the SMTP greeting message.
(Was the $e macro, see §34.8.65,
confSMTP_ LOGIN_MSG with the m4 technique.)
Specifies the location of the statistics file
(usually sendmail.st preceded by an
(Was the S option, see §34.8.66,
STATUS_FILE with the m4 technique.)
(safe) Ensures additional reliability by forcing all messages to
be queued, even if they could be directly delivered.
(Was the s option, see §34.8.67,
confSAFE_QUEUE with the m4 technique.)
Sets the default permissions (in octal) for created temporary files.
(Was the F option, see §34.8.68,
confTEMP_FILE_MODE with the m4 technique.)
Sets the time zone to that specified. If zone is absent,
imports the TZ variable from the environment.
If the entire option
is missing, the default is to unset the TZ environmental variable and
use the system default.
(Was the t option, see §34.8.69,
confTIME_ZONE with the m4 technique.)
Sets the timeout for an event to the interval specified. See the section "The Timeout Option" for details.
Tells sendmail to connect directly to the A record for
a host when the best MX record points to this host.
(Was the w option, see §34.8.71,
confTRY_NULL_MX_LIST with the m4 technique.)
Defines the format for the UUCP-style
(Was the $l macro, see §34.8.72,
confFROM_LINE with the m4 technique.)
Tells sendmail to check group write permissions
on files that it is taking addresses from, and to reject
those files (and hence the addresses)
when such group write permissions are found
confUNSAFE_GROUP_WRITES with the m4 technique).
(safe) Allows error notification
to be sent to the address listed in the
in addition to that sent to the envelope sender.
(Was the l option, see §34.8.74,
confUSE_ ERRORS_TO with the m4 technique.)
Specifies the location of the database file that will be
used for User Database lookups.
(Was the U option, see §34.8.75,
confUSERDB_SPEC with the m4 technique.)
(safe) Causes sendmail to run in verbose mode. (Was the v option, see §34.8.76.)