post - deliver a message

Post is the default program called by send to deliver the message in file to local and remote users. In fact, most of the features attributed to send in its manual page are performed by post, with send acting as a relatively simple preprocessor. Thus, it is post which parses the various header fields, appends “From:” and “Date:” lines, and interacts with the mail transport system. Post will not normally be called directly by the user.

Post searches the “To:”, “cc:”, “Bcc:”, “Fcc:”, and “Resent-xxx:” header lines of the specified message for destination addresses, checks these addresses for validity, and formats them so as to conform to ARPAnet Internet Message Format protocol, unless the -noformat flag is set. This will normally cause “@local-site” to be appended to each local destination address, as well as any local return addresses. The -width columns switch can be used to indicate the preferred length of the header components that contain addresses.

If a “Bcc:” field is encountered, its addresses will be used for delivery, and the “Bcc:” field will be removed from the message sent to sighted recipients. The blind recipients will receive an entirely new message with a minimal set of headers. Included in the body of the message will be a copy of the message sent to the sighted recipients. If -filter filterfile is specified, then this copy is filtered (re-formatted) by mhl prior to being sent to the blind recipients. Alternately, if the -mime switch is given, then post will use the MIME rules for encapsulation.

The -alias aliasfile switch can be used to specify a file that post should take aliases from. More than one file can be specified, each being preceded with -alias. In any event, the primary alias file is read first.

The -msgid switch indicates that a “Message-ID:” or “Resent-Message-ID:” field should be added to the header.

The -verbose switch indicates that the user should be informed of each step of the posting/filing process.

The -watch switch indicates that the user would like to watch the transport system's handling of the message (e.g., local and “fast” delivery).

Under normal circumstances, post constructs the “From:” line of the message from the user's login name, the full name from the GECOS field of the passwd file, and the fully-qualified name of the local machine (or the value of “localname” in mts.conf, if set). An example is “From: Dan Harkless <dan@machine.company.com>”. There are four ways to override these values, however. Note that they apply equally to “Resent-From:” lines in messages sent with dist.

The first way is GECOS-based username masquerading. If the “masquerade:” line in mts.conf contains “mmailid”, this processing is activated. If a user's GECOS field in the passwd file is of the form “Full Name <fakename>” then “fakename” will be used in place of the real username. For instance, a GECOS field of “Dan Harkless <Dan.Harkless>” would result in “From: Dan Harkless <Dan.Harkless@machine.company.com>”. Naturally if you were doing something like this you'd want to set up an MTA alias (e.g. in /etc/aliases) from, for instance, “Dan.Harkless” to “dan”.

The second way to override default construction of “From:” is to set the $SIGNATURE environment variable. This variable overrides the full name from the GECOS field, even if GECOS-based masquerading is being done. This processing is always active, and does not need to be enabled from mts.conf.

The third way is controlled by the “user_extension” value of “masquerade:” line of mts.conf. When that's turned on, setting the $USERNAME_EXTENSION environment variable will result in its value being appended the user's login name. For instance, if I set $USERNAME_EXTENSION to “+www”, my “From:” line will contain “Dan Harkless <dan+www@machine.company.com>” (or “Dan.Harkless+www” if I'm using mmailid masquerading as well). Recent versions of sendmail automatically deliver all mail sent to user+string to user. qmail has a similar feature which uses '-' as the delimiter by default, but can use other characters as well.

The fourth method of address masquerading is to specify a “From:” line manually in the message draft. It will be used as provided (after alias substitution), but normally, to discourage email forgery, the user's real address will be used in the SMTP envelope “From:” and in a “Sender:” header. However, if the “masquerade:” line of mts.conf contains “draft_from”, the SMTP envelope “From:” will use the address given in the draft “From:”, and there will be no “Sender:” header. This is useful in pretending to send mail “directly” from a remote POP3 account, or when remote email robots give improper precedence to the envelope “From:”. Note that your MTA may still reveal your real identity (e.g. sendmail's “X-Authentication-Warning:” header).

If nmh has been compiled with SASL support, the -sasl switch will enable the use of SASL authentication with the SMTP MTA. Depending on the SASL mechanism used, this may require an additional password prompt from the user (but the “.netrc” file can be used to store this password). -saslmech switch can be used to select a particular SASL mechanism, and the the -user switch can be used to select a authorization userid to provide to SASL other than the default.

Currently SASL security layers are not supported for SMTP. nmh's SMTP SASL code will always negotiate an unencrypted connection. This means that while the SMTP authentication can be encrypted, the subsequent data stream can not. This is in contrast to nmh's POP3 SASL support, where encryption is supported for both the authentication and the data stream.

^/etc/nmh/mts.conf~^nmh mts configuration file
^/etc/nmh/MailAliases~^global nmh alias file
^/usr/bin/mh/refile~^Program to process Fcc:s
^/usr/lib/mh/mhl~^Program to process Bcc:s

post does NOT consult the user's .mhprofile

mhmail(1), send(1), mh-mail(5), mh-alias(5), mh-tailor(5), Standard for the Format of ARPA Internet Text Messages (RFC-822)

`-alias' defaults to /etc/nmh/MailAliases
`-format'
`-nomime'
`-nomsgid'
`-noverbose'
`-nowatch'
`-width 72'
`-nofilter'

None

“Reply-To:” fields are allowed to have groups in them according to the 822 specification, but post won't let you use them.