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sendmail Desktop Reference

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The sendmail.cf File
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2.6 Options

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.

AliasFile= file [ , file , ...]

Defines the location (and optionally the type as type:file ) of the aliases file or files. (Was the A option, see §34.8.1, or define ALIAS_FILE with the m4 technique.)

AliasWait= interval

Specifies the interval sendmail will wait for the aliases database to rebuild. (Was the a option, see §34.8.2, or define confALIAS_WAIT with the m4 technique.)

AllowBogusHELO= [ True | False ]

(safe) allows sendmail to accept an SMTP HELO or EHLO that is not followed by a hostname (see §34.8.3).

AutoRebuildAliases= [ True | False ]

Allows sendmail to automatically rebuild the aliases database. (Was the D option, see §34.8.4, or define confAUTO_REBUILD with the m4 technique.)

BlankSub= char

Specifies the unquoted space replacement character char . (Was the B option, see §34.8.5, or define confBLANK_SUB with the m4 technique.)

CheckAliases= [ True | False ]

(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, or define confCHECK_ALIASES with the m4 technique.)

CheckpointInterval= number

(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, or define confCHECKPOINT_INTERVAL with the m4 technique.)

ClassFactor= factor

Sets the multiplication factor for calculating priority increments. (Was the z option, see §34.8.8, or define confWORK_CLASS_FACTOR with the m4 technique.)

ColonOkInAddr= [ True | False ]

(safe) tells sendmail to allow colons in addresses, thus disabling recognition of :; list addresses - DECnet :: is always allowed (see §34.8.9, or define confCOLON_OK_IN_ADDR with the m4 technique).

ConnectionCacheSize= number

Stipulates the number of simultaneous open SMTP connections sendmail will maintain during delivery. (Was the k option, see §34.8.10, or define confMCI_CACHE_SIZE with the m4 technique.)

ConnectionCacheTimeout= duration

Stipulates the duration of time any given open, but when idle, SMTP connection will be maintained. (Was the K option, see §34.8.11, or define confMCI_CACHE_ TIMEOUT with the m4 technique.)

ConnectionRateThrottle= number

Specifies the maximum number of incoming connections that will be accepted per second. Additional connections are accepted progressively more slowly (see §34.8.12, or define confCONNECTION_ RATE_THROTTLE with the m4 technique).

DaemonPortOptions= option = value [ , option = value , ...]

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; and SendSize is the size of the TCP/IP send buffer. (Was the O option, see §34.8.13, or define confDAEMON_ OPTIONS with the m4 technique.)

DefaultCharSet= set

(safe) Defines the character set that will be listed in the Content-Type: header, for MIME 8- to 7-bit conversion (see §34.8.14, or define confDEF_CHAR_ SET with the m4 technique).

DefaultUser= user [ : group ]

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, or define confDEF_ USER_ID with the m4 technique.)

DeliveryMode= mode

(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; or deferred to queue all mail without doing any DNS lookups. (Was the d option, see §34.8.16, or define confDELIVERY_MODE with the m4 technique.)

DialDelay= interval

(safe) specifies how long to sleep after a connection failure. If non-zero, sleeps that interval then tries again (see §34.8.17, or define confDIAL_DELAY with the m4 technique).

DontExpandCnames= [ True | False ]

Prevents CNAME expansion when looking up MX records (see §34.8.18, or define confDONT_ EXPAND_CNAMES with the m4 technique).

DontInitGroups= [ True | False ]

Suppresses use of the initgroups (3) call to look up additional group memberships (see §34.8.19, or define confDONT_INIT_GROUPS with the m4 technique).

DontPruneRoutes= [ True | False ]

Prevents sendmail from short-circuiting source routes. (Was the R option, see §34.8.20, or define confDONT_PRUNE_ROUTES with the m4 technique.)

DoubleBounceAddress= address

Specifies the address to which an error message should be sent if there is an error sending an error message (see §34.8.21, or define confDOUBLE_BOUNCE_ADDRESS with the m4 technique).

EightBitMode= how

(safe) specifies how to convert unlabeled MIME input. Select from: mimify to force conversion of 8BITMIME to 7-bit; pass to pass unlabeled 8-bit input through as-is; or strict to reject unlabeled 8-bit input. (Was the 8 option, see §34.8.22, or define confEIGHT_BIT_HANDLING with the m4 technique.)

ErrorHeader= description

(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, or define confERROR_MESSAGE with the m4 technique.)

ErrorMode= mode

(safe) specify mode of error handling. Select from: 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; or w to write errors to the sender's terminal screen. (Was the e option, see §34.8.24, or define confERROR_ MODE with the m4 technique.)

FallbackMXhost= host

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, or define confFALLBACK_MX with the m4 technique.)

ForkEachJob= [ True | False ]

Causes queue files to be processed individually to lessen the impact on small-memory machines. (Was the Y option, see §34.8.26, or define confSEPARATE_PROC with the m4 technique.)

ForwardPath= file [ : file : ...]

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, or define confFORWARD_PATH with the m4 technique.)

HelpFile= file

Specifies the location of the file that contains help messages for the SMTP (and ESMTP) HELP command, and usage for the -bt rule-testing command. (Was the H option, see §34.8.28, or define HELP_FILE with the m4 technique.)

HoldExpensive= [ True | False ]

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, or define confCON_ EXPENSIVE with the m4 technique.)

HostsFile= file

Specifies an alternative for the /etc/hosts file (see §34.8.30, or define confHOSTS_FILE with the m4 technique).

HostStatusDirectory= directory

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 (see §34.8.31, or define confHOST_STATUS_DIRECTORY with the m4 technique).

IgnoreDots= [ True | False ]

(safe) tells sendmail to ignore leading dots in the message body. (Was the i option, see §34.8.32, or define confIGNORE_DOTS with the m4 technique.)

LogLevel= level

(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; and 16-98 logs progressively more detailed debugging information. On the command line, you can only increase the logging level. (Was the L option, see §34.8.33, or define confLOG_LEVEL with the m4 technique.)

MatchGECOS= [ True | False ]

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, or define confMATCH_ GECOS with the m4 technique.)

MaxDaemonChildren= number

Specifies maximum number of children that sendmail will fork to process inbound connections. Does not limit forked children that process the queue (see §34.8.35, or define confMAX_DAEMON_CHILDREN with the m4 technique).

MaxHopCount= number

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, or define confMAX_HOP with the m4 technique.)

MaxMessageSize= size

Specifies the maximum size (in bytes) of an incoming message that sendmail will accept (see §34.8.37, or define confMAX_MESSAGE_SIZE with the m4 technique).

MaxQueueRunSize= number

(safe) specifies the maximum number of queued messages that sendmail will process from a queue in a given queue run (see §34.8.38, or define confMAX_QUEUE_RUN_SIZE with the m4 technique).

MeToo= [ True | False ]

(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 mailing list. (Was the m option, see §34.8.39, or define confME_TOO with the m4 technique.)

MinFreeBlocks= number

(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 command. (Was the b option, see §34.8.40, or define confMIN_FREE_BLOCKS with the m4 technique.)

MinQueueAge= interval

(safe) skips processing of a queued file if the last time it was processed is sooner than the interval specified (see §34.8.41, or define confMIN_ QUEUE_AGE with the m4 technique).

MustQuoteChars= characters

Allows sendmail to quote nonaddress characters in an address, as required by RFC822 (see §34.8.42).

NoRecipientAction= how

(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 Bcc: headers). Select from: add-apparently-to , which adds an Apparently-To: header; add-bcc , which adds an empty Bcc: header; add-to , which adds an empty To: header; add-undisclosed , which adds a To: undisclosed-recipients:; header; or none , which passes the message unchanged (see §34.8.43, or define confNO_RCPT_ACTION with the m4 technique).

OldStyleHeaders= [ True | False ]

(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, or define confOLD_STYLE_HEADERS with the m4 technique.)

OperatorChars= characters

Sets token-separation operators to the list of characters given. (Was the $o macro, see §34.8.45, or define confOPERATORS with the m4 technique.)

PostmasterCopy= address

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, or define confCOPY_ERRORS_TO with the m4 technique.)

PrivacyOptions= option [ , option , ...]

(safe) increases privacy and security of the daemon. Each option adds to earlier options. Select from: authwarnings , which enables X-Authentication-Warning: headers; 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; and 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; and noreceipts , which disables sending of return-receipt mail. (Was the p option, see §34.8.47, or define confPRIVACY_ FLAGS with the m4 technique.)

QueueDirectory= pathname

Specifies the full pathname of the queue directory. (Was the Q option, see §34.8.48, or define QUEUE_DIR with the m4 technique.)

QueueFactor= factor

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 formula, where load is the current load average, the message is delivered. (Was the q option, see §34.8.49, or define confQUEUE_FACTOR with the m4 technique.)

QueueLA= load

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, or define confQUEUE_LA with the m4 technique.)

QueueSortOrder= how

(safe) specifies how to presort the queue. Select from: host to sort by recipient host, lock status, and priority; priority for a simple sort of the message priorities; or time to sort based on submission time (see §34.8.51, or define confQUEUE_ SORT_ORDER with the m4 technique).

QueueTimeout= interval

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, use the Timeout.queuereturn option instead.)

RecipientFactor= factor

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, or define confWORK_RECIPIENT_FACTOR with the m4 technique.)

RefuseLA= load

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.)

ResolverOptions= arg [ arg ...]

Tunes DNS lookups by specifying an arg , or args, such as: +AAONLY , which turns on the AAONLY name server option (Authoritative Answers Only); and -DNSRCH , which turns off the DNSRCH name server option (search the domain path). (Was the I option, see §34.8.55, or define confBIND_OPTS with the m4 technique.)

RetryFactor= increment

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, or define confWORK_ TIME_FACTOR with the m4 technique.)

RunAsUser= user [ : group ]

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 (see §34.8.57, or define confRUN_AS_USER with the m4 technique).

SafeFileEnvironment= pathname

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 (see §34.8.58, or define confSAFE_ FILE_ENV with the m4 technique).

SaveFromLine= [ True | False ]

Prevents sendmail from removing UNIX mailbox-style From lines from input. (Was the f option, see §34.8.59, or define confSAVE_FROM_LINES with the m4 technique.)

SendMimeErrors= [ True | False ]

(safe) Tells sendmail it may return error messages (bounced mail notifications) in MIME format. (Was the j option, see §34.8.60, or define confMIME_ FORMAT_ERRORS with the m4 technique.)

ServiceSwitchFile= file

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 (see §34.8.61, or define confSERVICE_SWITCH_FILE with the m4 technique).

SevenBitInput= [ True | False ]

(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, or define confSEVEN_ BIT_INPUT with the m4 technique.)

SingleLineFromHeader= [ True | False ]

(safe) Tells sendmail to strip all newline characters from From: headers (see §34.8.63).

SingleThreadDelivery= [ True | False ]

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 (see §34.8.64, or define confSINGLE_THREAD_ DELIVERY with the m4 technique).

SmtpGreetingMessage= $j Sendmail $v ready at $b

Specifies the SMTP greeting message. (Was the $e macro, see §34.8.65, or define confSMTP_ LOGIN_MSG with the m4 technique.)

StatusFile= file

Specifies the location of the statistics file (usually sendmail.st preceded by an appropriate path). (Was the S option, see §34.8.66, or define STATUS_FILE with the m4 technique.)

SuperSafe= [ True | False ]

(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, or define confSAFE_QUEUE with the m4 technique.)

TempFileMode= mode

Sets the default permissions (in octal) for created temporary files. (Was the F option, see §34.8.68, or define confTEMP_FILE_MODE with the m4 technique.)

TimeZoneSpec= zone

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, or define confTIME_ZONE with the m4 technique.)

Timeout. event = interval

Sets the timeout for an event to the interval specified. See the section "The Timeout Option" for details.

TryNullMXList= [ True | False ]

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, or define confTRY_NULL_MX_LIST with the m4 technique.)

UnixFromLine= format

Defines the format for the UUCP-style From line. (Was the $l macro, see §34.8.72, or define confFROM_LINE with the m4 technique.)

UnsafeGroupWrites= [ True | False ]

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 (see §34.8.73, or define confUNSAFE_GROUP_WRITES with the m4 technique).

UseErrorsTo= [ True | False ]

(safe) Allows error notification to be sent to the address listed in the Errors-To: header in addition to that sent to the envelope sender. (Was the l option, see §34.8.74, or define confUSE_ ERRORS_TO with the m4 technique.)

UserDatabaseSpec= file

Specifies the location of the database file that will be used for User Database lookups. (Was the U option, see §34.8.75, or define confUSERDB_SPEC with the m4 technique.)

Verbose= [ True | False ]

(safe) Causes sendmail to run in verbose mode. (Was the v option, see §34.8.76.)