Deliver interactively (synchronously)

Deliver in background (asynchronously)

Queue only (don't deliver)

Seconds

Minutes

Hours

Days

Weeks

Small messages receive lower priorities than large messages, increasing the efficiency of the queue.

If the user includes a Precedence: field and value in a message, sendmail uses the value to select the message class from the configuration file. (Typical values might be “first-class” or “bulk.”)

This factor is set in the configuration file with the z option; its default value is 1800.

The number of recipients affects the load a message presents to the system. A message with a single recipient has a lower priority than one with a long recipient list.

This factor is set in the configuration file with the y option; its default value is 1000.

No logging

Major problems only

Message collections and failed deliveries

Successful deliveries

Messages being deferred (because a host is down, for example)

Normal message queue-ups

Unusual but benign incidents, such as trying to process a locked queue file

Log internal queue ID to external message ID mappings; useful for tracing a message as it travels among several hosts

Several messages of interest when debugging

Verbose information regarding the queue

Attempts to run a locked queue file

Monitor load average computation and process counting

Set operation mode to x. Operation modes are:

Use a different configuration file. sendmail runs as the invoking user (rather than root) when this flag is specified.

Set debugging flag (or range of flags) to the specified level. (The default is 1.) See “sendmail Debugging Flags”.

Set the full name of the sender to name. 

Set the name of the From person (the sender of the mail). This flag is ignored unless the user appears in the list of “trusted” users, or name is the same as the user's name.

Set the “hop count” to cnt. The hop count is incremented every time the mail is processed. When it reaches a limit, the mail is returned with an error message, the victim of an aliasing loop.

Ignore dots alone on line by themselves on incoming messages.

Set delivery status notification.

Don't do aliasing.

Set configuration option x to the specified value. These options are described in section “sendmail Configuration Options”.

Set message-receiving protocol. Use the protocol name or a combination of protocol and hostname, for example, UUCP:ucbvax.

Process the queued mail. If the time is given, sendmail will run through the queue at the specified interval to deliver queued mail; otherwise, it runs only once. See “Specifying the sendmail Queue Mode”.

Set the amount of message to be returned if delivery fails. For example, set full to return the full message, or hdrs for headers only.

An alternative and obsolete form of -f. 

Read the header for To:, Cc:, and Bcc: lines, and send the message to everyone listed in those lists. The Bcc: line is deleted before sending. Any addresses in the argument vector are deleted from the send list.

Set the initial user submission. For user agents like Mail or exmh, this should always be set. For network delivery agents like rmail, this should never be set.

Set the original envelope ID.

Go into verbose mode: Alias expansions are announced, and so on.

Logs all mailer traffic to logfile. Use only for stubborn debugging problems, because data piles up quickly.

Alternate freeze file is designated with file.

Use the named file as the alias file. If no file is specified, use an alias in the current directory.

If set, wait up to N minutes for an @:@ entry to exist in the alias database before starting up. If the entry does not appear in N minutes, rebuild the database (if the D option is also set) or issue a warning.

Set the blank substitution character to c. Unquoted spaces in addresses are replaced by this character.

Set the minimum number of free blocks needed to spool any message, while setting the maximum allowable message size. Defaults are 0 (zero) and infinite, respectively.

Check the queue file after N successful deliveries. This can be useful if you send to a long mailing list interrupted by system crashes, which would otherwise engender several duplicate deliveries.

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

Rebuild the alias database if necessary and possible. If this option is not set, sendmail will not rebuild the alias database until you explicitly request it to do so (by using sendmail -bi).

Deliver in mode x. These are the legal modes:

Add headers to error messages. If the value begins with /, the error header formats are read from the specified file.

Handle errors by using mode x. The values for x are:

Set the UNIX file mode to use when creating queue files and “frozen configuration” files.

Save UNIX style “From” lines at the front of headers. Normally these lines are assumed to be redundant and are discarded.

Match local names against the GECOS portion of the password file.

Set the default group ID for running mailers to n.

Specify the help file for SMTP.

Set the maximum times a message is allowed to hop before it is categorized as being in a loop.

Insist that the BIND name server be running to resolve hostnames and MX records. Treat ECONNREFUSED errors from the resolver as temporary failures. In general, you should set this option only if you are running the name server. Set this option if the /etc/hosts file does not include all known hosts or if you are using the MX (mail forwarding) feature of the BIND name server. The name server is still consulted even if this option is not set, but sendmail resorts to reading /etc/hosts if the name server is not available.

Do not interpret dots on a line by themselves as a message terminator.

Use this path to search for users' .forward file. The default is $z.forward, but can also be set as a sequence of paths separated by colons.

Send error messages in MIME format.

Define the maximum amount of time a cached connection is permitted to idle without activity. The timeout is given as a tagged number, with “s” for seconds, “m” minutes, “h” hours, “d” days, and “w” weeks. For example, “K1h30m” and “K90m” both set the timeout to one hour and thirty minutes.

Define the maximum number of cached open connections. The default is one; if set to zero, connections are closed immediately.

Set the log level to n. Possible values for n are these:

If there is an Errors-To: header, send any error messages to those addresses.

Set the macro x to value. This option can be used only from the command line.

Send to “me” (the sender) even if the sender is in an alias expansion.

Set the name of the home (local) network. If the name of a connecting host (determined by a call to gethostbyaddr()) is unqualified (contains no dots), a single dot and netname will be appended to sendmail's idea of the name of the connecting host.

Later, the argument of the SMTP HELO command from the connecting host will be checked against the name of the connecting host as determined above. If they do not match, Received: lines are augmented by the connecting hostname that sendmail has generated so that messages can be traced accurately.

Validate the right-hand side when building the alias database.

Assume that the headers may be in an old format, in which spaces delimit names. This option 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 written with commas between the names.

Add “postmaster” address addr to the Cc: list of all error messages.

Insist on privacy options to conform to SMTP protocols:

Use dir as the queue directory.

Use factor as the multiplier in the function to decide when to queue messages rather than attempting to send them. This value is divided by the difference between the current load average and the load average limit (x option) to determine the maximum message priority that will be sent.This value defaults to 10000.

Explicitly route to the first address in the route.

Cause a timeout on reads after time interval.

Log statistics in the named file. 

Be super-safe when running; that is, always instantiate the queue file, even if attempting immediate delivery. sendmail always instantiates the queue file before returning control to the client under any circumstances.

Set the queue timeout to time. After this interval, messages that have not been successfully sent are returned to the sender.

Set the local timezone, for example, PST8PDT.

Set the default user ID for mailers to n. Mailers without the S flag in the mailer definition run as this user.

Set host to act like a very low priority MX on every host.

Run in verbose mode.

If we are the best MX, try the host directly. This state is set by default.

Use load as the system load average limit when deciding whether to queue messages rather than attempting to send them.

When the system load average exceeds load, refuse incoming SMTP connections.

This factor is multiplied by the number of recipients and added to the priority. Therefore, this value penalizes messages with large numbers of recipients.

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.

This factor is multiplied by the message class (determined by the Precedence field in the user header and the precedence declaration lines in the configuration file) and subtracted from the priority. Therefore, messages with a higher class are favored.

This factor is added to the priority every time a message is processed. Therefore, this value penalizes messages that are processed frequently.

If the opening connection fails, sleep for sleeptime seconds and try again. Useful for dial-on-demand sites.

Set the behavior when there are no recipient headers (To:, Cc: or Bcc;) in the message to action. Possible values for action are these:

The aliases file in the berkeley db format.

The alias file in ndbm format.

Shell script for starting and stopping the sendmail daemon.

The configuration file in textual form.

The SMTP help file.

A text file that contains the names of all known “dead” hosts (hosts that no longer exist or cannot receive mail for some reason).

The configuration file for the sendmail.cf file.

Program that sendmail uses as the “local” mailer.

Prints a listing of the mail queue; using this file is equivalent to using the -bp flag to sendmail. 

A link to /usr/lib/sendmail; causes the alias database to be rebuilt. Running this program is equivalent to giving sendmail the -bi flag.

The text version of the alias file.

The sendmail program.

A statistics file; need not be present.

The directory in which the mail queue and temporary files reside.

Data files.

A file used when a unique ID is created.

Control (queue) files for messages.

Temporary versions of the qf files, used during queue-file rebuild.

A transcript of the current session.

Print information about sendmail version.

Show known names for local host.

Dump delivery agents.

Print network address of each interface.

Have printav() print addresses of elements.

Show mail “From” address for locally generated mail.

Print exit status and envelope flags.

Trace state of enoughspace().

Print arguments to tick() calls.

Print arguments to setevent() and clrevent() calls.

Print event queue on tick() call.

Indicate call to savemail() or returntosender() error processing.

Trace states in savemail() state machine.

Print information on envelope assigned to queue file.

Print selected queue-file name.

Print intermediate queue-file name selections.

Print various information about resolver calls.

Return fully qualified canonical hostname to getcanonname(3).

Trace local hostnames that were dropped.

Print hostname being tried in getcanonname(3).

Answer yes or no to the hostname being tried in getcanonname(3).

Turn on MX resolver debugging when it sends back the wrong type.

Show results from gethostbyaddr() call.

Print message delivery information.

Log information about mail program used by call to openmailer().

Show the user and group IDs running during delivery.

Display remotename() input and output.

sendall()—Print addresses being sent to.

sendall()—Print each address in loop looking for failure.

sendall()—Print who gets the error.

Indicate commaize() calls.

Indicate port or socket number used by getrequests().

Indicate when getrequests() forks or returns.

Set DEBUG socket option in getrequests().

Indicate host, address, and socket being connected to in makeconnection().

Set DEBUG socket option in makeconnection().

Show SMTP chatter.

Suspend sendmail after reading each SMTP reply.

Display parseaddr() input and output.

Show rewrite rule-set subroutine calls/returns and input/output, and display run-time macro expansions.

Indicate rewrite subroutine call from inside rewrite rule.

Display rewrite results.

Indicate rule failures.

Indicate rule matches and display address-rewrite steps.

Show rewrite substitutions.

Display elements in pattern and subject.

Display any invalid address before parsing with prescan().

Display address typed in before parsing with prescan().

Show “To” list designations.

Show recipient designations/duplicate suppression.

Show recipient password-match processing.

Print alias and forward transformations and errors.

Include file, self-reference, error on home.

Print detailed aliaslookup() information.

Warn if user tries to run included files owned by another user.

Warn if a user changes uid/gid when included files are read.

Trace user database transactions.

Print matches that are a result of fuzzy searches.

Indicate end of headers when collecting a message.

Print arguments to eatfrom() calls.

Indicate when adding an Apparently-To header to the message.

Trace processing of headers.

Indicate call to chompheader() and header to be processed.

Display collected header.

Display crackaddr() input/output.

Trace how headers are generated and how they are skipped.

Display macro definitions.

Display macro expansions.

Show symbol table processing.

Show symbol table hash function result.

Display options as set.

Show rewrite class loading.

Show words added to class.

Show map opens and failures.

Show the results of map opens.

Trace map lookups.

Indicate queueing of messages and display queue contents.

Display queue control file contents.

Display information about message-controlling user.

Display the queue ordering.

Indicate orderq() failure to open control file.

Trace writable() calls.

Trace calls to the user-configurable check_rule sets.

Indicate setsender() calls.

Indicate dropenvelope() calls.

Don't remove transcript files (qxAAXXXXX files).

Indicate call to disconnect(); print I/O file descriptors.

Don't perform disconnect.

Print information about map lookups inside rewrite().

Print information about MX record lookups.