There are a number of "random" options that can be set from a configuration file. Options are represented by a single character or by multiple character names. The syntax for the single character names of is:

Oxvalue

This sets option x to be value. Depending on the option, value may be a string, an integer, a boolean (with legal values t, T, f, or F; the default is TRUE), or a time interval.

The multiple character or long names use this syntax:

O Longname=argument

This sets the option Longname to be argument. The long names are beneficial because they are easier to interpret than the single character names.

Not all processing options have single character names associated with them. In the list below the multiple character name is presented first followed by the single character syntax enclosed in parentheses.

AliasFile (Afile)

Specify possible alias files.

AliasWait (a N)

If set, wait up to N minutes for an "@:@" entry to exist in the aliases(4) database before starting up. If it does not appear in N minutes, issue a warning. Defaults to 10 minutes.

AllowBogusHELO

Allow a HELO SMTP command that does not include a host name. By default this option is disabled.

BadRcptThrottle=N

If set and more than the specified number of recipients in a single SMTP envelope are rejected, sleep for one second after each rejected RCPT command.

BlankSub (Bc)

Set the blank substitution character to c. Unquoted spaces in addresses are replaced by this character. Defaults to SPACE (that is, no change is made).

CheckAliases (n)

Validate the RHS of aliases when rebuilding the aliases(4) database.

CheckpointInterval (CN)

Checkpoints the queue every N (default 10) addresses sent. If your system crashes during delivery to a large list, this prevents retransmission to any but the last N recipients.

ClassFactor (zfact)

The indicated factor fact is multiplied by the message class (determined by the Precedence: field in the user header and the P lines in the configuration file) and subtracted from the priority. Thus, messages with a higher Priority: are favored. Defaults to 1800.

ClientPortOptions

Set client SMTP options. The options are key=value pairs. Known keys are:

Addr Address Mask

Address Mask defaults to INADDR_ANY. The address mask can be a numeric address in dot notation or a network name.

Family

Address family (defaults to INET).

Listen

Size of listen queue (defaults to 10).

Port

Name/number of listening port (defaults to smtp).

RcvBufSize

The size of the TCP/IP receive buffer.

SndBufSize

The size of the TCP/IP send buffer.

Modifier

Options (flags) for the daemon. Can be:

h

Use name of interface for HELO command.

If h is set, the name corresponding to the outgoing interface address (whether chosen by means of the Connection parameter or the default) is used for the HELO/EHLO command.

ColonOkInAddr

If set, colons are treated as a regular character in addresses. If not set, they are treated as the introducer to the RFC 822 "group" syntax. This option is on for version 5 and lower configuration files.

ConnectionCacheSize (kN)

The maximum number of open connections that are be cached at a time. The default is 1. This delays closing the current connection until either this invocation of sendmail needs to connect to another host or it terminates. Setting it to 0 defaults to the old behavior, that is, connections are closed immediately.

ConnectionCacheTimeout (Ktimeout)

The maximum amount of time a cached connection is permitted to idle without activity. If this time is exceeded, the connection is immediately closed. This value should be small (on the order of ten minutes). Before sendmail uses a cached connection, it always sends a NOOP (no operation) command to check the connection; if this fails, it reopens the connection. This keeps your end from failing if the other end times out. The point of this option is to be a good network neighbor and avoid using up excessive resources on the other end. The default is five minutes.

ConnectionRateThrottle

The maximum number of connections permitted per second. After this many connections are accepted, further connections are delayed. If not set or <= 0, there is no limit.

ControlSocketName

Name of the control socket for daemon management. A running sendmail daemon can be controlled through this Unix domain socket. Available commands are: help, restart, shutdown, and status. The status command returns the current number of daemon children, the free disk space (in blocks) of the queue directory, and the load average of the machine expressed as an integer. If not set, no control socket is available. For the sake of security, this Unix domain socket must be in a directory which is accessible only by root; /var/spool/mqueue/.smcontrol is recommended for the socket name.

DaemonPortOptions (Ooptions)

Set server SMTP options. The options are key=value pairs. Known keys are:

Name

User-definable name for the daemon (defaults to "Daemon#"); used for error messages and logging.

Addr

Address mask (defaults INADDR_ANY)

The address mask may be a numeric address in dot notation or a network name.

Family

Address family (defaults to INET)

Listen

Size of listen queue (defaults to 10)

Modifier

Options (flags) for the daemon; can be a sequence (without any delimiters) of:

a

Require authentication.

b

Bind to interface through which mail has been received.

c

Perform hostname canonification (.cf).

f

Require fully qualified hostname (.cf).

h

Use name of interface for HELO command.

u

Allow unqualified addresses (.cf).

C

Do not perform hostname canonification.

E

Disallow ETRN (see RFC 2476).

Name

User-definable name for the daemon (defaults to Daemon#); used for error messages and logging.

Port

Name/number of listening port (defaults to smtp)

ReceiveSize

The size of the TCP/IP receive buffer.

SendSize

The size of the TCP/IP send buffer.

sendmail listens on a new socket for each occurrence of the DaemonPortOptions option in a configuration file.

DataFileBufferSize

Set the threshold, in bytes, before a memory-bases queue data file becomes disk-based. The default is 4096 bytes

DeadLetterDrop

Defines the location of the system-wide dead.letter file, formerly hard-coded to /var/tmp/dead.letter. If this option is not set (the default), sendmail does not attempt to save to a system-wide dead.letter file in the event it cannot bounce the mail to the user or postmaster. Instead, it renames the qf file as it has in the past when the dead.letter file could not be opened.

DefaultCharSet

Set the default character set to use when converting unlabeled 8 bit input to MIME.

DefaultUser (ggid) or (uuid)

Set the default group ID for mailers to run in to gid or set the default userid for mailers to uid. Defaults to 1. The value can also be given as a symbolic group or user name.

DelayLA=LA

When the system load average exceeds LA, sendmail sleeps for one second on most SMTP commands and before accepting connections.

DeliverByMin=time

Set minimum time for Deliver By SMTP Service Extension (RFC 2852). If 0, no time is listed, if less than 0, the extension is not offered, if greater than 0, it is listed as minimum time for the EHLO keyword DELIVERBY.

DeliveryMode (dx)

Deliver in mode x. Legal modes are:

i

Deliver interactively (synchronously).

b

Deliver in background (asynchronously).

d

Deferred mode -- database lookups are deferred until the actual queue run.

q

Just queue the message (deliver during queue run).

Defaults to b if no option is specified, i if it is specified but given no argument (that is, Od is equivalent to Odi).

DialDelay

If a connection fails, wait this many seconds and try again. Zero means "do not retry".

DontBlameSendmail

If set, override the file safety checks. This compromises system security and should not be used. See http://www.sendmail.org/tips/DontBlameSendmail.html for more information.

DontExpandCnames

If set, $[ ... $] lookups that do DNS-based lookups do not expand CNAME records.

DontInitGroups

If set, the initgroups(3C) routine is never be invoked. If you set this, agents run on behalf of users only have their primary (/etc/passwd) group permissions.

DontProbeInterfaces

If set, sendmail does not insert the names and addresses of any local interfaces into the $=w class. If set, you must also include support for these addresses, otherwise mail to addresses in this list bounce with a configuration error.

DontPruneRoutes (R)

If set, do not prune route-addr syntax addresses to the minimum possible.

DoubleBounceAddress

If an error occurs when sending an error message, send that "double bounce" error message to this address.

EightBitMode (8)

Use 8-bit data handling. This option requires one of the following keys. The key can selected by using just the first character, but using the full word is better for clarity.

mimify

Do any necessary conversion of 8BITMIME to 7-bit.

pass

Pass unlabeled 8-bit input through as is.

strict

Reject unlabeled 8-bit input.

ErrorHeader (Efile/message)

Append error messages with the indicated message. If it begins with a slash, it is assumed to be the pathname of a file containing a message (this is the recommended setting). Otherwise, it is a literal message. The error file might contain the name, email address, and/or phone number of a local postmaster who could provide assistance to end users. If the option is missing or NULL, or if it names a file which does not exist or which is not readable, no message is printed.

ErrorMode (ex)

Dispose of errors using mode x. The values for x are:

e

Mail back errors and give 0 exit status always.

m

Mail back errors.

p

Print error messages (default).

q

No messages, just give exit status.

w

Write back errors (mail if user not logged in).

FallbackMXhost (Vfallbackhost)

If specified, the fallbackhost acts like a very low priority MX on every host. This is intended to be used by sites with poor network connectivity.

FastSplit

If set to a value greater than zero (the default is one), it suppresses the MX lookups on addresses when they are initially sorted, that is, for the first delivery attempt. This usually results in faster envelope splitting unless the MX records are readily available in a local DNS cache. To enforce initial sorting based on MX records set FastSplit to zero. If the mail is submitted directly from the command line, then the value also limits the number of processes to deliver the envelopes; if more envelopes are created they are only queued up and must be taken care of by a queue run. Since the default submission method is by way of SMTP (either from a MUA or by way of the MSP), the value of FastSplit is seldom used to limit the number of processes to deliver the envelopes.

ForkEachJob (Y)

If set, deliver each job that is run from the queue in a separate process. Use this option if you are short of memory, since the default tends to consume considerable amounts of memory while the queue is being processed.

ForwardPath (Jpath)

Set the path for searching for users' .forward files. The default is $z/.forward. Some sites that use the automounter may prefer to change this to /var/forward/$u to search a file with the same name as the user in a system directory. It can also be set to a sequence of paths separated by colons; sendmail stops at the first file it can successfully and safely open. For example, /var/forward/$u:$z/.forward searches first in /var/forward/ username and then in ~username/.forward (but only if the first file does not exist). Refer to the NOTES section for more information.

HelpFile (Hfile)

Specify the help file for SMTP.

HoldExpensive (c)

If an outgoing mailer is marked as being expensive, don't connect immediately.

HostsFile

Set the file to use when doing "file" type access of host names.

HostStatusDirectory

If set, host status is kept on disk between sendmail runs in the named directory tree. If a full path is not used, then the path is interpreted relative to the queue directory.

IgnoreDots (i)

Ignore dots in incoming messages. This is always disabled (that is, dots are always accepted) when reading SMTP mail.

LogLevel (Ln)

Set the default log level to n. Defaults to 9.

(Mxvalue)

Set the macro x to value. This is intended only for use from the command line.

MailboxDatabase

Type of lookup to find information about local mail boxes, defaults to pw which uses getpwnam(3C). Other types can be introduced by adding them to the source code, see libsm/mbdb.c for details.

MatchGECOS (G)

Try to match recipient names using the GECOS field. This allows for mail to be delivered using names defined in the GECOS field in /etc/passwd as well as the login name.

MaxDaemonChildren

The maximum number of children the daemon permits. After this number, connections are rejected. If not set or <=0, there is no limit.

MaxHopCount (hN)

The maximum hop count. Messages that have been processed more than N times are assumed to be in a loop and are rejected. Defaults to 25.

MaxMessageSize

The maximum size of messages that are accepted (in bytes).

MaxMimeHeaderLength=M[/N]

Sets the maximum length of certain MIME header field values to M characters. For some of these headers which take parameters, the maximum length of each parameter is set to N if specified. If /N is not specified, one half of M is used. By default, these values are 0, meaning no checks are done.

MaxQueueChildren=N

When set, this limits the number of concurrent queue runner processes to N. This helps to control the amount of system resources used when processing the queue. When there are multiple queue groups defined and the total number of queue runners for these queue groups would exceed MaxQueueChildren then the queue groups are not all run concurrently. That is, some portion of the queue groups run concurrently such that MaxQueueChildren is not be exceeded, while the remaining queue groups are run later (in round robin order). See MaxRunnersPerQueue.

MaxQueueRunSize

If set, limit the maximum size of any given queue run to this number of entries. This stops reading the queue directory after this number of entries is reached; job priority is not used. If not set, there is no limit.

MaxRunnersPerQueue=N

This sets the default maximum number of queue runners for queue groups. Up to N queue runners work in parallel on a queue group's messages. This is useful where the processing of a message in the queue might delay the processing of subsequent messages. Such a delay can be the result of non-erroneous situations such as a low bandwidth connection. The can be overridden on a per queue group basis by setting the Runners option. The default is 1 when not set.

MeToo (M)

Send to me too, even if I am in an alias expansion.

MaxRecipientsPerMessage

If set, allow no more than the specified number of recipients in an SMTP envelope. Further recipients receive a 452 error code and are deferred for the next delivery attempt.

MinFreeBlocks (bN/M)

Insist on at least N blocks free on the file system that holds the queue files before accepting email by way of SMTP. If there is insufficient space, sendmail gives a 452 response to the MAIL command. This invites the sender to try again later. The optional M is a maximum message size advertised in the ESMTP EHLO response. It is currently otherwise unused.

MinQueueAge

The amount of time a job must sit in the queue between queue runs. This allows you to set the queue run interval low for better responsiveness without trying all jobs in each run. The default value is 0.

MustQuoteChars

Characters to be quoted in a full name phrase. &,;:\()[] are quoted automatically.

NiceQueueRun

The priority of queue runners. See nice(1).

NoRecipientAction

Set action if there are no legal recipient files in the message. The legal values are:

add-apparently-to

Add an Apparently-to: header with all the known recipients (which may expose blind recipients).

add-bcc

Add an empty Bcc: header.

add-to

Add a To: header with all the known recipients (which may expose blind recipients).

add-to-undisclosed

Add a To: undisclosed-recipients: header.

none

Do nothing, leave the message as it is.

OldStyleHeaders (o)

Assume that the headers may be in old format, that is, spaces delimit names. This actually turns on an adaptive algorithm: if any recipient address contains a comma, parenthesis, or angle bracket, it is assumed that commas already exist. If this flag is not on, only commas delimit names. Headers are always output with commas between the names.

OperatorChars or $o

Defines the list of characters that can be used to separate the components of an address into tokens.

PidFile

Filename of the pid file. The default is /var/run/sendmail.pid. The filename is macro-expanded before it is opened.

PostmasterCopy (Ppostmaster)

If set, copies of error messages are sent to the named postmaster. Only the header of the failed message is sent. Since most errors are user problems, this is probably not a good idea on large sites, and arguably contains all sorts of privacy violations, but it seems to be popular with certain operating systems vendors.

PrivacyOptions (popt,opt,...)

Set privacy options. Privacy is really a misnomer; many of these are just a way of insisting on stricter adherence to the SMTP protocol.

The goaway pseudo-flag sets all flags except noreceipts, restrictmailq, restrictqrun, restrictexpand, noetrn, and nobodyreturn. If mailq is restricted, only people in the same group as the queue directory can print the queue. If queue runs are restricted, only root and the owner of the queue directory can run the queue. The restrict-expand pseudo-flag instructs sendmail to drop privileges when the -bv option is given by users who are neither root nor the TrustedUser so users cannot read private aliases, forwards, or :include: files. It adds the NonRootSafeAddr to the "DontBlame-Sendmail" option to prevent misleading unsafe address warnings. It also overrides the -v (verbose) command line option to prevent information leakage. Authentication Warnings add warnings about various conditions that may indicate attempts to fool the mail system, such as using an non-standard queue directory.

The options can be selected from:

authwarnings

Put X-Authentication-Warning: headers in messages.

goaway

Disallow essentially all SMTP status queries.

needexpnhelo

Insist on HELO or EHLO command before EXPN.

needmailhelo

Insist on HELO or EHLO command before MAIL.

needvrfyhelo

Insist on HELO or EHLO command before VRFY.

noetrn

Disallow ETRN entirely.

noexpn

Disallow EXPN entirely.

noreceipts

Prevent return receipts.

nobodyreturn

Do not return the body of a message with DSNs.

novrfy

Disallow VRFY entirely.

public

Allow open access.

restrictexpand

Restrict -bv and -v command line flags.

restrictmailq

Restrict mailq command.

restrictqrun

Restrict -q command line flag.

ProcessTitlePrefix string

Prefix the process title shown on "/usr/ucb/ps auxww" listings with string. The string is macro processed.

QueueDirectory (Qdir)

Use the named dir as the queue directory.

QueueFactor (qfactor)

Use factor as the multiplier in the map function to decide when to just queue up jobs rather than run them. This value is divided by the difference between the current load average and the load average limit (xflag) to determine the maximum message priority to be sent. Defaults to 600000.

QueueFileMode=mode

Default permissions for queue files (octal). If not set, sendmail uses 0600 unless its real and effective uid are different in which case it uses 0644.

QueueLA (xLA)

When the system load average exceeds LA, just queue messages (that is, do not try to send them). Defaults to eight times the number of processors online when sendmail starts.

QueueSortOrder=algorithm

Sets the algorithm used for sorting the queue. Only the first character of the value is used. Legal values are host (to order by the name of the first host name of the first recipient), filename (to order by the name of the queue file name), time (to order by the submission/creation time), random (to order randomly), modification (to order by the modification time of the qf file (older entries first)), and priority (to order by message priority). Host ordering makes better use of the connection cache, but may tend to process low priority messages that go to a single host over high priority messages that go to several hosts; it probably shouldn't be used on slow network links. Filename and modification time ordering saves the overhead of reading all of the queued items before starting the queue run. Creation (submission) time ordering is almost always a bad idea, since it allows large, bulk mail to go out before smaller, personal mail, but may have applicability on some hosts with very fast connections. Random is useful if several queue runners are started by hand which try to drain the same queue since odds are they are working on different parts of the queue at the same time. Priority ordering is the default.

QueueTimeout (Trtime/wtime)

Set the queue timeout to rtime. After this interval, messages that have not been successfully sent are returned to the sender. Defaults to five days (5d). The optional wtime is the time after which a warning message is sent. If it is missing or 0, then no warning messages are sent.

RecipientFactor (yfact)

The indicated factor fact is added to the priority (thus lowering the priority of the job) for each recipient, that is, this value penalizes jobs with large numbers of recipients. Defaults to 30000.

RefuseLA (XLA)

When the system load average exceeds LA, refuse incoming SMTP connections. Defaults to 12 times the number of processors online when sendmail starts.

ResolverOptions (I)

Tune DNS lookups.

RetryFactor (Zfact)

The indicated factor fact is added to the priority every time a job is processed. Thus, each time a job is processed, its priority is decreased by the indicated value. In most environments this should be positive, since hosts that are down are all too often down for a long time. Defaults to 90000.

RrtImpliesDsn

If this option is set, a "Return-Receipt-To:" header causes the request of a DSN, which is sent to the envelope sender as required by RFC 1891, not to the address given in the header.

RunAsUser

If set, become this user when reading and delivering mail. Intended for use of firewalls where users do not have accounts.

SafeFileEnvironment

If set, sendmail does a chroot into this directory before writing files.

SaveFromLine (f)

Save Unix-style From lines at the front of headers. Normally they are assumed redundant and discarded.

SendMimeErrors (j)

If set, send error messages in MIME format (see RFC 2045 and RFC 1344 for details). If disabled, sendmail does not return the DSN keyword in response to an EHLO and does not do Delivery Status Notification processing as described in RFC 1891.

ServiceSwitchFile

Defines the path to the service-switch file. Since the service-switch file is defined in the Solaris operating environment this option is ignored.

SevenBitInput (7)

Strip input to seven bits for compatibility with old systems. This should not be necessary.

SharedMemoryKey

Key to use for shared memory segment; if not set (or 0), shared memory is not be used. If this option is set, sendmail can share some data between different instances. For example, the number of entries in a queue directory or the available space in a file system. This allows for more efficient program execution, since only one process needs to update the data instead of each individual process gathering the data each time it is required.

SingleLineFromHeader

If set, From: lines that have embedded newlines are unwrapped onto one line.

SingleThreadDelivery

If this option and the HostStatusDirectory option are both set, use single thread deliveries to other hosts.

SmtpGreetingMessage or $e

The initial SMTP greeting message.

StatusFile (Sfile)

Log statistics in the named file. By default, this is /etc/mail/sendmail.st. As root, you must touch(1) this file to enable mailstats(1).

SuperSafe (s)

This option can be set to True, False, or Interactive. If set to True, sendmail is set to super-safe when running things, that is, always instantiate the queue file, even if you are going to attempt immediate delivery. sendmail always instantiates the queue file before returning control to the client under any circumstances. This should really always be set to True. The Interactive value has been introduced in 8.12 and can be used together with DeliveryMode=i. It skips some synchronization calls which are effectively doubled in the code execution path for this mode.

TempFileMode (Fmode)

The file mode for queue files.

Timeout (rtimeouts)

Timeout reads after time interval. The timeouts argument is a list of keyword=value pairs. All but command apply to client SMTP. For backward compatibility, a timeout with no keyword= part is set all of the longer values. The recognized timeouts and their default values, and their minimum values specified in RFC 1123 section 5.3.2 are:

aconnect

all connections for a single delivery attempt [0, unspecified]

command

command read [1h, 5m]

connect

initial connect [0, unspecified]

control

complete control socket transaction [2m, none]

datablock

data block read [1h, 3m]

datafinal

reply to final . in data [1h, 10m]

datainit

reply to DATA command [5m, 2m]

fileopen

file open [60sec, none]

helo

reply to HELO or EHLO command [5m, none]

hoststatus

host retry [30m, unspecified]

iconnect

first attempt to connect to a host [0, unspecified]

ident

IDENT protocol timeout [5s, none]

initial

wait for initial greeting message [5m, 5m]

lhlo

wait for reply to an LMTP LHLO command [2m, unspecified].

mail

reply to MAIL command [10m, 5m]

misc

reply to NOOP and VERB commands [2m, none]

queuereturn

undeliverable message returned [5d]

queuewarn

deferred warning [4h]

quit

reply to QUIT command [2m, none]

rcpt

reply to RCPT command [1h, 5m]

resolver.retrans

Resolver's retransmission time interval (in seconds) [varies]. Sets both Timeout.resolver.retrans.first and Timeout.resolver.retrans.normal.

resolver.retrans.first

Resolver's retransmission time interval (in seconds) for the first attempt to deliver a message [varies].

resolver.retrans.normal

Resolver's retransmission time interval (in seconds) for all look-ups except the first delivery attempt [varies].

resolver.retry

Number of times to retransmit a resolver query [varies]. Sets both Timeout.resolver.retry.first and Timeout.resolver.retry.normal.

resolver.retry.first

Number of times to retransmit a resolver query for the first attempt to deliver a message [varies].

resolver.retry.normal

Number of times to retransmit a resolver query for all look-ups except the first delivery attempt [varies].

rset

reply to RSET command [5m, none]

TimeZoneSpec (ttzinfo)

Set the local time zone info to tzinfo, for example, "PST8PDT ". Actually, if this is not set, the TZ environment variable is cleared (so the system default is used); if set but null, the user's TZ variable is used, and if set and non-null, the TZ variable is set to this value.

TrustedUser

The user parameter can be a user name (looked up in the passwd map) or a numeric user id. Trusted user for file ownership and starting the daemon. If set, generated alias databases and the control socket (if configured) are automatically owned by this user.

TryNullMXList (w)

If you are the "best" (that is, lowest preference) MX for a given host, you should normally detect this situation and treat that condition specially, by forwarding the mail to a UUCP feed, treating it as local, or whatever. However, in some cases (such as Internet firewalls) you may want to try to connect directly to that host as though it had no MX records at all. Setting this option causes sendmail to try this. The downside is that errors in your configuration are likely to be diagnosed as "host unknown" or "message timed out" instead of something more meaningful. This option is deprecated.

UnixFromLine or $l

The "From " line used when sending to files or programs.

UnsafeGroupWrites

If set, group-writable :include: and .forward files are considered "unsafe", that is, programs and files cannot be directly referenced from such files.

UseErrorsTo (l)

If there is an Errors-To: header, send error messages to the addresses listed there. They normally go to the envelope sender. Use of this option causes sendmail to violate RFC 1123. This option is not recommended and deprecated.

UseMSP

Use as mail submission program, that is., allow group writable queue files if the group is the same as that of a set-group-id sendmail binary.

UserDatabaseSpec (U)

Defines the name and location of the file containing User Database information.

Verbose (v)

Run in verbose mode. If this is set, sendmail adjusts the HoldExpensive and DeliveryMode options so that all mail is delivered completely in a single job so that you can see the entire delivery process. The Verbose option should never be set in the configuration file; it is intended for command line use only.

XscriptFileBufferSize

Set the threshold, in bytes, before a memory-bases queue transcript file becomes disk-based. The default is 4096 bytes.

If the first character of the user name is a vertical bar, the rest of the user name is used as the name of a program to pipe the mail to. It may be necessary to quote the name of the user to keep sendmail from suppressing the blanks from between arguments.

If invoked as newaliases, sendmail rebuilds the alias database, so long as the /etc/mail/aliases* files are owned by root and root has exclusive write permission. If invoked as mailq, sendmail prints the contents of the mail queue.