Send email from the command line

Sometimes you need to send an email from the console or from a bash script. Here are a few use cases.

• mail – simple email: echo "BODY MESSAGE" | mail -s "Subject" rcpt@some-domain.com

• mail – with attachment: echo "BODY MESSAGE" | mail -s "Subject" -a attachment.txt rcpt@some-domain.com

• sendmail – simple email:

  sendmail email@some-domain.com <<EOF
  Subject: Test Subject
  From: test@some-domain.com
  
  Email body.
  EOF

• sendmail – HTML content:

  sendmail email@some-domain.com <<EOF
  Subject: Test Subject
  From: test@some-domain.com
  MIME-Version: 1.0
  Content-Type: text/html
  
  <html>
    <head>
      <title>My email</title>
    </head>
    <body>
      <h2>Here will be your message body</h2>
    </body>
  </html>
  EOF

• sendmail – HTML with an attached picture:

  mailpart="$(uuidgen)"
  sendmail -t <<EOM
  To: email@some-domain.com
  Subject: Test Subject
  From: test@some-domain.com
  MIME-Version: 1.0
  Content-Type: multipart/mixed; boundary="${mailpart}"
  
  --${mailpart}
  Content-Type: text/html; charset=ISO-8859-15
  Content-Transfer-Encoding: 7bit
  
  <html>
    <head>
      <title>My email</title>
    </head>
    <body>
      <img src="cid:part1.06090408.01060107" alt="">
    </body>
  </html>
  
  --${mailpart}
  Content-Type: image/png; name="filename.png"
  Content-Transfer-Encoding: base64
  Content-ID: <part1.06090408.01060107>
  Content-Disposition: inline; filename="filename.png"
  
  $(base64 /path/to/filename.png)
  --${mailpart}--
  EOM

• sendmail – HTML with an embedded picture and a plain-text alternative:

  mailpart="$(uuidgen)"
  mailpartBody="$(uuidgen)"
  
  /usr/sbin/sendmail -t <<EOF
  Subject: Test Subject
  From: email@some-domain.com
  To: email@some-domain.com
  Content-Type: multipart/related; type="multipart/alternative"; boundary="${mailpart}"
  MIME-Version: 1.0
  
  --${mailpart}
  Content-Type: multipart/alternative; boundary="${mailpartBody}"
  
  --${mailpartBody}
  Content-Type: text/plain
  Content-Transfer-Encoding: 7bit
  
  Here we have message-body
  
  --${mailpartBody}
  Content-Type: text/html; charset="utf-8"
  Content-Transfer-Encoding: 7bit
  
  <html>
    <head>
      <title>My email</title>
    </head>
    <body>
      <h3>Here we have message-body</h3>
      <img src="cid:image.png@some-domain.com" alt="">
    </body>
  </html>
  
  --${mailpartBody}--
  
  --${mailpart}
  Content-ID: <image.png@some-domain.com>
  Content-Type: image/png; name=image.png
  Content-Disposition: inline; filename=image.png
  Content-Transfer-Encoding: base64
  
  $(base64 image.png)
  
  --${mailpart}--
  EOF