Utility to replace /usr/bin/mail for sending email on macOS.

mail.py is a Python 3 script for sending email messages from the command line. Unlike /usr/bin/mail, it can be used only to send mail, not to receive messages. However, it can be used to send multipart messages with plain text and/or HTML message parts, and the smtp server to use can be set with an environment variable.

Bash scripts that sent email using /usr/bin/mail on macOS stopped working after an Apple security update in January 2019. PHP scripts that used the PHP Mailer package stopped working too. But Python's smtplib continued to work okay.

I was unable to get any useful information about the issue from Apple support and on https://developer.apple.com (hundreds of views; zero replies), so I wrote this as a workaround.

• This is a Python 3 application. The command assumes the interpreter is /usr/local/bin/python3. Edit the first line of the code if this path needs to be changed. Alternatively, invoke as python3 /path/to/mail.py options... .
• The environment variable SMTP_SERVER specifies the hostname of the server that will relay the message. If SMTP_SERVER is not set, the environment variable HOSTNAME will be used instead.
• The -f or --from_addr command line option may be used to specify the sender’s email address. The default value is $USER@$HOSTNAME. Valid formats are:
  • Real Name <username@domain>
  • username@domain
• If neither a plain text file (-p) nor a HTML file (-h) is specified, a plain text message body is read from stdin.
• The default Subject: is “Test Message”

$ mail.py -?
usage: mail.py [-?] [-s SUBJECT] [-c CC_ADDR [CC_ADDR ...]]
               [-b BCC_ADDR [BCC_ADDR ...]] [-r REPLY_ADDR] [-h HTML_FILE]
               [-p PLAINTEXT_FILE] [-d DEBUGLEVEL] [-f FROM_ADDR]
               to_addr [to_addr ...]

Simplified replacement for /usr/bin/mail

positional arguments:
  to_addr

optional arguments:
  -?, --help
  -s SUBJECT, --subject SUBJECT
  -c CC_ADDR [CC_ADDR ...], --cc_addr CC_ADDR [CC_ADDR ...]
  -b BCC_ADDR [BCC_ADDR ...], --bcc_addr BCC_ADDR [BCC_ADDR ...]
  -r REPLY_ADDR, --reply_addr REPLY_ADDR
  -h HTML_FILE, --html_file HTML_FILE
  -p PLAINTEXT_FILE, --plaintext_file PLAINTEXT_FILE
  -d DEBUGLEVEL, --debuglevel DEBUGLEVEL
  -f FROM_ADDR, --from_addr FROM_ADDR