mailbot — A MIME-aware autoresponder utility


mailbot [options] {program} [arg...]

In .mailfilter:

if (/^Subject: *info/)
     cc "| mailbot -t /usr/share/autoresponse/info -d autoresponsedb \
            -A 'From:' /usr/bin/sendmail -f ''"


mailbot reads an E-mail message on standard input and creates an E-mail message replying to the original message's sender. A program is specified as an argument to mailbot after all of mailbot options. program is expected to read the created autoreply on its standard input, and mail it. If program is not specified, mailbot runs 'sendmail -f ""'.

mailbot has several options for suppressing duplicate autoresponse messages. If mailbot chooses not to send an autoresponse, it quietly terminates without running program. The autoresponse is optionally formatted as a MIME delivery status notification.

The text of the autoresponse is specified by the -t or the -m argument. Either one is required. Everything else is optional. The only exception is the -T replydraft option, which requires the -l option instead of either -t or -m. The default behavior is to send an autoresponse unless the original message has the "Precedence: junk" or the "Precedence: bulk" header, or the "Precedence: list" header, or the "List-ID:" header, or if its MIME content type is "multipart/report" (this is the MIME content type for delivery status notifications). The -M option formats the the autoresponse itself as a MIME delivery status notification.


-A "header: value"

Add a header to the autoresponse. Multiple -A options are allowed. In most situations, the -A option must be used to set the From: header in the autogenerated response.


Address the autoresponse to address, which must be an RFC 2822 address. By default mailbot takes the autoresponse address from the From: (or the Reply-To:) header in the original message. -f, if present, overrides and explicitly sets the autoresponse address. "address" must immediately follow the -f option without an intervening space (it's a single command line argument). An -f option without an address takes the address from the SENDER environment variable.

-t filename

Read text autoresponse from filename, which must contain a plain text message in flowed-text format. In a flowed-text-formatted message, each line that ends with a space character indicates that the line logically flows into the next line. This allows the message to be reformatted for any shown display width.


Messages in languages (see the -c option) which use spaces as word delimiters must have two spaces at the end of a flowed line. The last space on a flowed line is logically removed, and the first space separates the last word on the previous line from the first word on the next line. Otherwise, the two words will not have a logical space between them if they get repositioned as part of adjusting the message's width for display.

Messages in ideographic languages that do not use spaces as word delimiters need only one space trailing a flowed line.


The trailing whitespace has no visual impact when shown by software that does not implemented flowed text format, and always displays messages using their original width.

-c charset

Set the autoresponse's MIME character set to charset. Run mailbot without any arguments to see the default character set.

-m filename

Read a MIME autoresponse from filename. This is similar to the -t option, except that filename contains MIME headers, followed by a blank line, and the corresponding MIME content. The contents of filename are inserted in the autoresponse without further processing.

The specified file must contain the Content-Type header specifying the text/plain MIME type, with the format=flowed, delsp=yes, and the charset attributes, which override the -c parameter. If the specified file has a Content-Transfer-Encoding header it must be either 7bit or 8bit, it may not be quoted-printable. mailbot always drops any existing Content-Transfer-Encoding header and always adds the Content-Transfer-Encoding: 8bit header, even with the -m, since the salutation inserted into the message includes the sender's name, which may contain 8-bit characters. Example:

Content-Type: text/plain; format=flowed; delsp=yes; charset="iso-8859-1"

Mary had a little lamb,  
Its fleece was white as snow.  
And everywhere Mary went,  
The lamb was sure to go.


When the -m option is specified mailbot ignores the locale's character set and formats the autoreply according to the character set read from the Content-Type header.

-M address

Format the autoresponse as a delivery status notification (RFC 1894). address is an RFC 2822 E-mail address that generates the DSN. Note that the -A option should still be used in addition to -M in order to set the From: header on the autoresponse. -M sets the DSN address only. The -M option automatically sets -T replydsn

-R type

Specify the feedback report type, with type set to abuse, fraud, other, or virus. Must be used together with -T feedback or -T replyfeedback.

-T format

Set the reply format. format must be one of the following values:

  • reply - the default reply format.

  • replyall - like reply, except also puts the recipients in the original message's To: and Cc: headers into the Cc: header of the generated reply.

  • replydsn - like reply, except the message is formatted as a delivery status notification.

  • replydraft - like reply, with the text of the autoresponse coming from a maildir specified by the -l option. See Autoreplies from a maildir folder, below.

  • forward - attach the original message as forwarded text.

  • forwardatt - attach the original message as a forwarded message attachment.

  • feedback - generate an Email Feedback Report message (see RFC 5965). The -R option is required when this is specified.

  • replyfeedback - like feedback, but also adds a To: header, addressed to the original message's sender.


Do not quote the contents of the original message in the message created by reply, replyall, replydsn, feedback, and replyfeedback options.


The original message gets quoted, in the absence of this option, only if the original message was formatted as plain text. mailbot is unable to quote an original message which was formatted as HTML, or any other non-plaintext format.


For replydsn, feedback, and replyfeedback options, the convention is to attach the original message, or only its headers, separately; so this option should always be specified for these three reply formats.


Attach the entire message, for replydsn, feedback, and replyfeedback, instead of only its headers.


Generate a reply (reply-formats) to the address listed in any Errors-To or Return-Path header, if present, instead of the From header.

-S salutation

Use the given salutation in the reply. The default value is %F writes:. The following substitutions are recognized in the salutation string:

  • %% - an explicit % character.

  • %n - a newline character.

  • %C - the X-Newsgroup: header from the original message.

  • %N - the Newsgroups: header from the original message.

  • %i - the Message-ID: header from the original message.

  • %f - the original message's sender's address.

  • %F - the original message's sender's name.

  • %S - the Subject: header from the original message

  • %d - the original message's date, in the local timezone.

  • %{...}d - use strftime() to format the original message's date. A plain %d is equivalent to %{%a, %d %b %Y %H:%M:%S %z}d.

All other characters in the salutation string are left as is.

-F marker

When generating a forward, use the marker to separate the forwarded message from the autoreply text, instead of the default --- Forwarded message ---

-r addrlist

addrlist is a comma-separated list of RFC 2822 E-mail addresses. mailbot sends an autoresponse only if the original message has at least one of the specified addresses in any To: or Cc: header.

-d filename

Create a small database, filename, that keeps track of senders' E-mail addresses, and prevent duplicate autoresponses going to the same address (suppress autoresponses going back to the same senders, for subsequent received messages). The -d option is only available if maildrop has GDBM/DB extensions enabled.

-D x

Do not send duplicate autoresponses (see the -d option) for at least x days (default: 1 day). The -d option creates a database of E-mail addresses and the times an autoresponse was last mailed to them. Another autoresponse to the same address will not be mailed until at least the amount of time specified by the -D option has elapsed.

-s "subject"

Set the Subject: header on the autoresponse to subject.


Show the resulting message, do not send it. Used for debugging purposes.

--feedback-original-envelope-id "<envelopeid>", --feedback-original-mail-from "<mailfrom>", --feedback-reporting-mta "dns; hostname", --feedback-source-ip aaa.bbb.ccc.ddd, --feedback-incidents n, --feedback-authentication-results "results", --feedback-original-rcpt-to "<rcptto>", --feedback-reported-domain

Optional parameters to include in the feedback report generated by feedback and replyfeedback. mailbot always adds Arrival-Date with the current time, as well as Version and User-Agent.

--feedback-authentication-results, --feedback-original-rcpt-to and --feedback-reported-domain may be specified more than once.

-l maildir

Specifies the maildir for the -T replydraft option. See Autoreplies from a maildir folder, below.

Autoreplies from a maildir folder

In .mailfilter:

cc "| mailbot -T replydraft -l './Maildir/.Vacation' \
        -d autoresponsedb \
        -A 'From:' /usr/bin/sendmail -f ''"
to "./Maildir"

The -T replydraft reply format takes the content of the autoresponse from the most recent message in a maildir. The -l option specifies the maildir. The above example takes the message from $HOME/Maildir/.Drafts which should be a maildir (with the usual cur, new, and tmp subdirectories). It would typically get created by Courier-IMAP as a folder named Vacation.

This makes it possible to install autoreplies via an IMAP client by creating a folder named Vacation, and copying a message into it. The contents of the message become the autoresponse.

If the named maildir does not exist, or is empty, mailbot does nothing. If the named maildir has more than one message, the most recent message gets used.

The above example uses additional mailbot options to suppress duplicate autoresponses, and to set the From: header on the autoresponse.