curl can be used to send emails with SMTP

  local email_body=$(cat <<- PANCAKE
 From: ${SMTP_FROM}
 To: ${SMTP_TO}
 Subject: BACKUP SCRIPT FAILED

 $0 backup script failed on ${HOSTNAME}
 Exit code: ${exit_code}
 Failed at line: ${line_number}

 $(journalctl -o cat --user _SYSTEMD_INVOCATION_ID=${invocation_id} || true)
 PANCAKE
  )
  ## TODO: see above

  # Send email via authenticated SMTP using curl
  echo "${email_body}" | curl -s --url "${SMTP_URL}" \
    --ssl-reqd \
    --mail-from "${SMTP_FROM}" \
    --mail-rcpt "${SMTP_TO}" \
    --user "${SMTP_USERNAME}:${SMTP_PASSWORD}" \
    --upload-file -
  }

When on a random CLI though my personal preference though is still to use telnet as the commands are easily memorized and there’s something more natural about typing the email out and then sending it.

(Checks docs)

Oh.