Sending mail from a Bash shell script

Question

I am writing a Bash shell script for Mac that sends an email notification by opening an automator application that sends email out with the default mail account in Mail.app. The automator application also attaches a text file that the script has written to. The problems with this solution are

1. It is visible in the GUI when sending
2. It steals focus if Mail is not the current application
3. It is dependent on Mail.app's account setup being valid in the future

I figure to get around those shortcomings I should send the mail directly from the script by entering SMTP settings, address to send to, etc. directly in the script. The catch is I would like to deploy this script on multiple computers (10.5 and 10.6) without enabling Postfix on the computer. Is it possible to do this in the script so it will run on a base Mac OS X install of 10.5. and 10.6?

Update: I've found the -bs option for Sendmail which seems to be what I need, but I'm at a loss of how to specify settings.

Also, to clarify, the reason I'd like to specify SMTP settings is that mails from localhost on port 25 sent out via Postfix would be blocked by most corporate firewalls, but if I specify the server and an alternate port I won't run into that problem.

Answer 1

I whipped this up for the challenge. If you remove the call to 'dig' to obtain the mail relay, it is a 100% native Bash script.

#!/bin/bash
MAIL_FROM="[e-mail]"
RCPT_TO="[e-mail]"
MESSAGE=message.txt
SMTP_PORT=25
SMTP_DOMAIN=${RCPT_TO##*@}

index=1
while read PRIORITY RELAY
do
    RELAY[$index]=$RELAY
    ((index++))
done < <( dig +short MX $SMTP_DOMAIN )

RELAY_COUNT=${#RELAY[@]}
SMTP_COMMANDS=( "HELO $HOSTNAME" "MAIL FROM: <$MAIL_FROM>" "RCPT TO: <$RCPT_TO>" "DATA" "." "QUIT" )
SMTP_REPLY=([25]=OK [50]=FAIL [51]=FAIL [52]=FAIL [53]=FAIL [54]=FAIL [55]=FAIL [45]=WAIT [35]=DATA [22]=SENT)

for (( i = 1 ; i < RELAY_COUNT ; i++ ))
do
    SMTP_HOST="${RELAY[$i]}"
    echo "Trying relay [$i]: $SMTP_HOST..."
    exec 5<>/dev/tcp/$SMTP_HOST/$SMTP_PORT
    read HELO <&5
    echo GOT: $HELO
    for COMMAND_ORDER in 0 1 2 3 4 5 6 7
    do
            OUT=${SMTP_COMMANDS[COMMAND_ORDER]}
            echo SENDING: $OUT
            echo -e "$OUT\r" >&5

            read -r REPLY <&5
            echo REPLY: $REPLY
            # CODE=($REPLY)
            CODE=${REPLY:0:2}
            ACTION=${SMTP_REPLY[CODE]}
            case $ACTION in
                    WAIT )          echo Temporarily Fail
                                                    break
                                                    ;;
                    FAIL )          echo Failed
                                                    break
                                                    ;;
                    OK )                            ;;
                    SENT )          exit 0
                                                    ;;
                    DATA )          echo Sending Message: $MESSAGE
                                                    cat $MESSAGE >&5
                                                    echo -e "\r" >&5
                                                    ;;
                    * )         echo Unknown SMTP code $CODE
                                                    exit 2
            esac
    done
done

Answer 2

There is a program called Sendmail.

You probably don't want to use the -bs command unless you are sending it as raw SMTP like Martin's example. -bs is for running an SMTP server as a deamon. Sendmail will send directly to the receiving mail server (on port 25) unless you override it in the configuration file. You can specify the configuration file by the -C paramter.

In the configuration, you can specify a relay server (any mail server or sendmail running -bs on another machine)

Using a properly configured relay server is good idea because when IT manages mail servers they implement SPF and domain keys. That keeps your mail out of the junk bin.

If port 25 is blocked you are left with two options.

1. Use the corporate SMTP server.
2. Run sendmail -bd on a machine outside of the corporate firewall that listens on a port other than 25.

I believe you can add configuration parameters on the command line. What you want is the SMART_HOST option. So call Sendmail like sendmail -OSMART_HOST=nameofhost.com.

Answer 3

Probably the only way you could do this, while keeping the program self-sufficient, is if you have direct access to an SMTP server from the clients.

If you do have direct access to an SMTP server you can use the SMTP example from wikipedia and turn it into something like this:

#!/bin/bash
telnet smtp.example.org 25 <<_EOF
HELO relay.example.org
MAIL FROM:<[e-mail]>
RCPT TO:<[e-mail]>
DATA
From: Joe <[e-mail]>
To: Jane <[e-mail]>
Subject: Hello

Hello, world!
.
QUIT
_EOF

To handle errors I would redirect the output from telnet to a file and then grep that for a "success message" later. I am not sure what format the message should be, but I see something like "250 2.0.0 Ok: queued as D86A226C574" in the output from my SMTP server. This would make me grep for "^250.*queued as".

Answer 4

Try mtcmail. Its a fairly complete email sender, completely standalone.

Answer 5

Since Mac OS X includes Python, consider using a Python script instead of a Bash script. I haven't tested the sending portion, but it follows the standard example.

Python script

# Settings

SMTP_SERVER = 'mail.myisp.com'
SMTP_PORT = 25
SMTP_USERNAME = 'myusername'
SMTP_PASSWORD = '$uper$ecret'
SMTP_FROM = '[e-mail]'
SMTP_TO = '[e-mail]'

TEXT_FILENAME = '/script/output/my_attachment.txt'
MESSAGE = """This is the message
to be sent to the client.
"""

# Now construct the message
import smtplib, email
from email import encoders
import os

msg = email.MIMEMultipart.MIMEMultipart()
body = email.MIMEText.MIMEText(MESSAGE)
attachment = email.MIMEBase.MIMEBase('text', 'plain')
attachment.set_payload(open(TEXT_FILENAME).read())
attachment.add_header('Content-Disposition', 'attachment', filename=os.path.basename(TEXT_FILENAME))
encoders.encode_base64(attachment)
msg.attach(body)
msg.attach(attachment)
msg.add_header('From', SMTP_FROM)
msg.add_header('To', SMTP_TO)

# Now send the message
mailer = smtplib.SMTP(SMTP_SERVER, SMTP_PORT)
# EDIT: mailer is already connected
# mailer.connect()
mailer.login(SMTP_USERNAME, SMTP_PASSWORD)
mailer.sendmail(SMTP_FROM, [SMTP_TO], msg.as_string())
mailer.close()

I hope this helps.

Answer 6

Here is a simple Ruby script to do this. Ruby ships on the Mac OS X versions you mentioned.

Replace all the bits marked 'replace'. If it fails, it returns a non-zero exit code and a Ruby back trace.

require 'net/smtp'

SMTPHOST = 'replace.yoursmtpserver.example.com'
FROM = '"Your Email" <[e-mail]>'

def send(to, subject, message)
  body = <<EOF
From: #{FROM}
To: #{to}
Subject: #{subject}

#{message}
EOF
  Net::SMTP.start(SMTPHOST) do |smtp|
    smtp.send_message body, FROM, to
  end
end

send('[e-mail]', 'testing', 'This is a message!')

You can embed this in a Bash script like so:

ruby << EOF
 ... script here ...
EOF

For some other ways to send Ruby emails, see Stack Overflow question How do I send mail from a Ruby program?.

You can use other languages that ship with Mac OS X as well:

• How do I send email with Perl?
• Sending HTML email using Python