101 lines
3.1 KiB
Markdown
101 lines
3.1 KiB
Markdown
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# Emailing with Curl
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`curl` is an amazing networking tool. It can even automate sending emails!
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You'll need a app password or real password to login to your email account
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## Email just a file
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For the most basic email, we can stuff the headers into the email file itself.
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Here's a basic example
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```bash
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cat <<EMAIL email.txt
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From: Emiliko Mirror <emiliko@gmail.com>
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To: Emiliko Mirror <emiliko@cs.ox.ac.uk>
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Subject: Sleep triggered on $(hostname)
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Date: $(date)
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Dear me,
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The system went to sleep! I thought I should notify my gmail account, so here
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I am.
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cheers,
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Emiliko
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EMAIL
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curl --silent --ssl-reqd \
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--url 'smtps://smtp.gmail.com:465' \
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--user 'emiliko@cs.ox.ac.uk:<my-password-here>' \
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--mail-from 'emiliko@cs.ox.ac.uk' \
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--mail-rcpt 'emiliko@gmail.com' \
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--upload-file email.txt
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```
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The `From:` - `Date:` headers at the top are very important. Gmail seems to
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insert them automatically if they're missing, though other mail providers
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require them
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If you use 2fa, you'll need to [obtain an app
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password](https://support.google.com/accounts/answer/185833?hl=en) instead
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## Email with attachments
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We can also `CC`, `BCC` and attach files with our curl emails
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Attachments need a MIME type for the file, which is easiest obtained with the
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`file` command. In this example, we also remove the headers from the email file,
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opting to use the more explicit `-H` curl option
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```bash
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declare -r attach_file=mirrors_house.png
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declare -r mime_type="$(file --mime-type "$attach_file" | sed 's/.*: //')"
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cat <<EMAIL >email.txt
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Dear classmates,
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I just bought a new house! Check out the picture I attached below
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OMGOMGOMG, I'm so excited!
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cheers,
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Kate Mirror
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EMAIL
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curl --silent --ssl-reqd \
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--url 'smtps://smtp.fastmail.com:465' \
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--user 'kate%40mirror.house:<my-password>' \
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--mail-from "kate@mirror.house" \
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--mail-rcpt 'emiliko@cs.ox.ac.uk' \
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--mail-rcpt 'lou@lou.me' \
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--mail-rcpt 'louis@louis.me' \
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-F '=(;type=multipart/mixed' \
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-F "=$(cat email.txt);type=text/plain" \
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-F "file=@${attach_file};filename=home.png;type=${mime_type};encoder=base64" \
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-F '=)' \
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-H "From: Kate Mirror <kate@mirror.house>" \
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-H "Subject: Check out my new place!" \
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-H "To: Emiliko Mirror <emiliko@cs.ox.ac.uk>" \
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-H "CC: Lou Mirror <lou@lou.me>" \
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-H "Date: $(date)"
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```
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Notice that for `BCC` the user isn't mentioned in `-H` at all, though still gets
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a `--mail-rcpt`
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Oddly, some mail servers seem sensitive to the filename field. My university
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server would consistently bounce emails when I tried to have a filename field.
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Consider removing it to use the file's actual name
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## Further reading
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- [A basic official guide](https://everything.curl.dev/usingcurl/smtp)
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- [Sending a simple email with
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curl](https://stackoverflow.com/questions/14722556/using-curl-to-send-email)
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- [An example on using the -F option with
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curl](https://blog.ambor.com/2021/08/using-curl-to-send-e-mail-with.html)
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- [Backup of the above on
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github](https://github.com/ambanmba/send-ses/blob/main/send-ses.sh)
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- [A hit at using the filename field in
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forums](https://stackoverflow.com/questions/15127732/change-name-of-upload-file-in-curl)
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