sendEmail
Overview
섹션 제목: “Overview”sendEmail is a lightweight, cross-platform command-line SMTP email client that enables sending emails directly from the terminal. It supports authentication, TLS/SSL encryption, attachments, and HTML content, making it essential for security testing, automated reporting, and authorized phishing assessments during penetration tests.
Key Capabilities:
- Send emails via SMTP without a mail client
- Support for TLS and SSL encryption
- SMTP authentication (basic and advanced)
- File attachments and embedded content
- HTML and plain text emails
- Batch email sending
- Certificate validation control
- Cross-platform compatibility (Linux, macOS, BSD, Windows)
Installation
섹션 제목: “Installation”From Source
섹션 제목: “From Source”# Clone or download sendEmail
git clone https://github.com/mogul/sendEmail.git
cd sendEmail
# Or download standalone script
wget http://www.sendEmail.org/sendEmail-v1.56.tar.gz
tar xzf sendEmail-v1.56.tar.gz
cd sendEmail-v1.56
# Make executable
chmod +x sendEmailVia Package Manager
섹션 제목: “Via Package Manager”# Kali Linux (pre-installed)
sendEmail -h
# Debian/Ubuntu
apt-get update
apt-get install sendemail
# macOS
brew install sendEmail
# Arch Linux
pacman -S sendEmailInstall Perl Dependencies (if needed)
섹션 제목: “Install Perl Dependencies (if needed)”# sendEmail is a Perl script, requires Perl
which perl
perl --version
# Install required Perl modules
cpan Net::SMTP::SSL
cpan Net::SMTP::TLS
cpan IO::Socket::SSL
# Or using apt
apt-get install libnet-smtp-ssl-perl
apt-get install libnet-smtp-tls-perlVerify Installation
섹션 제목: “Verify Installation”sendEmail -v
sendEmail -h
which sendEmailBasic Usage
섹션 제목: “Basic Usage”Send Simple Email
섹션 제목: “Send Simple Email”# Basic email sending
sendEmail -f sender@example.com \
-t recipient@example.com \
-s smtp.gmail.com:587 \
-u "Subject Line" \
-m "Email body text"Send with Authentication
섹션 제목: “Send with Authentication”# Send via SMTP with credentials
sendEmail -f sender@gmail.com \
-t recipient@example.com \
-s smtp.gmail.com:587 \
-xu sender@gmail.com \
-xp "password" \
-u "Subject" \
-m "Message body" \
-o tls=yesSend with Attachment
섹션 제목: “Send with Attachment”# Send email with file attachment
sendEmail -f sender@example.com \
-t recipient@example.com \
-s smtp.example.com:587 \
-u "Important Document" \
-m "Please find attached" \
-a /path/to/file.pdf
# Multiple attachments
sendEmail -f sender@example.com \
-t recipient@example.com \
-s smtp.example.com:587 \
-a file1.pdf file2.xlsx file3.zip \
-m "Files attached"Common sendEmail Commands
섹션 제목: “Common sendEmail Commands”| Command | Purpose |
|---|---|
-f ADDRESS | From email address (required) |
-t ADDRESS | To email address (required) |
-cc ADDRESS | Carbon copy address |
-bcc ADDRESS | Blind carbon copy |
-s HOST:PORT | SMTP server and port (required) |
-u SUBJECT | Email subject line |
-m MESSAGE | Email body message |
-a FILE | Attach file (can use multiple times) |
-xu USERNAME | SMTP username for authentication |
-xp PASSWORD | SMTP password |
-o tls=yes | Enable TLS encryption |
-o ssl=yes | Enable SSL encryption |
-c FILE | Use configuration file |
-v | Verbose output |
-q | Quiet mode |
Practical Examples
섹션 제목: “Practical Examples”Gmail SMTP Configuration
섹션 제목: “Gmail SMTP Configuration”# Send via Gmail (requires app-specific password)
sendEmail -f username@gmail.com \
-t recipient@example.com \
-s smtp.gmail.com:587 \
-xu username@gmail.com \
-xp "app_specific_password" \
-u "Test Email" \
-m "This is a test email from Gmail" \
-o tls=yes
# Note: Gmail requires 2FA app password, not regular passwordOutlook/Office 365 Configuration
섹션 제목: “Outlook/Office 365 Configuration”# Send via Office 365/Outlook
sendEmail -f user@company.onmicrosoft.com \
-t recipient@example.com \
-s smtp.office365.com:587 \
-xu user@company.onmicrosoft.com \
-xp "password" \
-u "Company Email" \
-m "Message body" \
-o tls=yesLocal SMTP Server (No Auth)
섹션 제목: “Local SMTP Server (No Auth)”# Send via local mail server
sendEmail -f admin@internal.local \
-t user@internal.local \
-s localhost:25 \
-u "Status Report" \
-m "Daily system report"HTML Email
섹션 제목: “HTML Email”# Send HTML content
sendEmail -f sender@example.com \
-t recipient@example.com \
-s smtp.example.com:587 \
-u "HTML Email Test" \
-m '<html><body><h1>Hello</h1><p>This is HTML content</p></body></html>' \
-o message-content-type=htmlEmail with Multiple Recipients
섹션 제목: “Email with Multiple Recipients”# Multiple recipients
sendEmail -f sender@example.com \
-t user1@example.com \
-t user2@example.com \
-cc supervisor@example.com \
-bcc admin@example.com \
-s smtp.example.com:587 \
-u "Multi-recipient email" \
-m "Sent to multiple recipients"Advanced Techniques
섹션 제목: “Advanced Techniques”Batch Email Sending
섹션 제목: “Batch Email Sending”# Create recipient list
cat > recipients.txt << 'EOF'
user1@example.com
user2@example.com
user3@example.com
EOF
# Send to multiple addresses
while read email; do
sendEmail -f sender@example.com \
-t "$email" \
-s smtp.example.com:587 \
-xu username \
-xp password \
-u "Personalized Subject" \
-m "Message body" \
-o tls=yes
done < recipients.txtConfiguration File
섹션 제목: “Configuration File”# Create configuration file
cat > email.conf << 'EOF'
from=sender@example.com
to=recipient@example.com
cc=cc@example.com
subject=Test Email
message=This is the email body
smtp=smtp.example.com:587
username=sender@example.com
password=secretpassword
tls=yes
verbose=yes
EOF
# Use configuration file
sendEmail -c email.confEmail with Custom Headers
섹션 제목: “Email with Custom Headers”# Add custom headers
sendEmail -f sender@example.com \
-t recipient@example.com \
-s smtp.example.com:587 \
-u "Subject" \
-m "Body" \
-o "header-custom-header:custom-value"Read Message from File
섹션 제목: “Read Message from File”# Create email body in file
cat > email_body.txt << 'EOF'
Dear Recipient,
This is a formatted email message
sent from the command line.
Best regards,
Security Team
EOF
# Send with file content
sendEmail -f sender@example.com \
-t recipient@example.com \
-s smtp.example.com:587 \
-u "File-based Message" \
-m "$(cat email_body.txt)"Automated Report Sending
섹션 제목: “Automated Report Sending”# Generate and send report daily
cat > send_daily_report.sh << 'EOF'
#!/bin/bash
# Generate report
REPORT_FILE="/tmp/daily_report_$(date +%Y%m%d).txt"
cat > "$REPORT_FILE" << 'REPORT'
DAILY SECURITY REPORT
=====================
Date: $(date)
Scan Results: [Data]
Alerts: [Data]
REPORT
# Send via email
sendEmail -f admin@company.com \
-t security-team@company.com \
-s smtp.company.com:587 \
-xu admin@company.com \
-xp "password" \
-u "Daily Security Report" \
-m "$(cat $REPORT_FILE)" \
-a "$REPORT_FILE" \
-o tls=yes
EOF
chmod +x send_daily_report.sh
# Schedule with cron
echo "0 9 * * * /path/to/send_daily_report.sh" | crontab -Security Testing Scenarios
섹션 제목: “Security Testing Scenarios”Phishing Simulation (Authorized)
섹션 제목: “Phishing Simulation (Authorized)”# Create phishing simulation email (with authorization)
sendEmail -f it-security@company.com \
-t employee@company.com \
-s smtp.company.com:587 \
-xu admin \
-xp password \
-u "Important Security Update Required" \
-m '<html><body>
<p>Click here to update your password:</p>
<a href="http://internal-test.local/password-reset">Update Password</a>
</body></html>' \
-o message-content-type=html \
-o tls=yesCredential Stuffing Test (Lab Environment)
섹션 제목: “Credential Stuffing Test (Lab Environment)”# Test multiple credentials against SMTP server
for cred in user1:pass1 user2:pass2 user3:pass3; do
USERNAME=$(echo $cred | cut -d: -f1)
PASSWORD=$(echo $cred | cut -d: -f2)
sendEmail -f test@example.com \
-t test@example.com \
-s target-smtp.local:587 \
-xu "$USERNAME" \
-xp "$PASSWORD" \
-u "Test" \
-m "Testing credentials" \
-o tls=yes 2>&1 | grep -i "success\|error"
doneProof of Concept - Email Spoofing
섹션 제목: “Proof of Concept - Email Spoofing”# Test email spoofing (open relay) - authorized lab only
sendEmail -f boss@company.com \
-t attacker@attacker.com \
-s open-relay-server:25 \
-u "Spoofed Email Test" \
-m "This email appears to come from the boss"Email Template Examples
섹션 제목: “Email Template Examples”Professional Report Format
섹션 제목: “Professional Report Format”cat > report_email.txt << 'EOF'
SECURITY ASSESSMENT REPORT
==========================
Period: [Date Range]
Client: [Organization]
Assessment Type: [Type of Test]
EXECUTIVE SUMMARY
-----------------
[Summary of findings]
VULNERABILITIES IDENTIFIED
---------------------------
[Vulnerability details]
RECOMMENDATIONS
----------------
[Security improvements]
NEXT STEPS
----------
[Follow-up actions]
EOF
sendEmail -f assessor@company.com \
-t client@example.com \
-s smtp.gmail.com:587 \
-xu assessor@gmail.com \
-xp "password" \
-u "Security Assessment Report - [Date]" \
-m "$(cat report_email.txt)" \
-a security_report.pdf \
-o tls=yesIncident Alert Format
섹션 제목: “Incident Alert Format”cat > incident_alert.txt << 'EOF'
SECURITY INCIDENT ALERT
======================
Severity: [HIGH/MEDIUM/LOW]
Time Detected: [Timestamp]
Affected Systems: [List]
Description: [Details]
Action Required: [Instructions]
Contact: [Escalation contact]
EOF
sendEmail -f security-ops@company.com \
-t incident-response@company.com \
-cc ciso@company.com \
-s smtp.company.com:587 \
-xu security-ops \
-xp password \
-u "[ALERT] Incident Detected" \
-m "$(cat incident_alert.txt)" \
-o tls=yesIntegration with Other Tools
섹션 제목: “Integration with Other Tools”Chain with System Commands
섹션 제목: “Chain with System Commands”# Get system information and email
SYSTEM_INFO=$(uname -a)
DISK_USAGE=$(df -h)
MEMORY_INFO=$(free -h)
sendEmail -f admin@company.com \
-t admin@company.com \
-s localhost:25 \
-u "System Report" \
-m "System: $SYSTEM_INFO
Disk: $DISK_USAGE
Memory: $MEMORY_INFO"Combine with Backup Status
섹션 제목: “Combine with Backup Status”# Send backup status email
BACKUP_STATUS=$(rsync -av /data /backup 2>&1)
sendEmail -f backup@company.com \
-t admin@company.com \
-s smtp.company.com:587 \
-xu backup \
-xp password \
-u "Backup Report - $(date +%Y-%m-%d)" \
-m "$(echo "$BACKUP_STATUS" | tail -20)" \
-o tls=yesEmail Penetration Test Results
섹션 제목: “Email Penetration Test Results”# Email scan results
NMAP_RESULTS=$(nmap -sV target.local)
sendEmail -f pentester@company.com \
-t client@example.com \
-s smtp.company.com:587 \
-u "Penetration Test Results" \
-m "Scan results attached" \
-a nmap_results.txt \
-o tls=yesTroubleshooting
섹션 제목: “Troubleshooting”Authentication Failed
섹션 제목: “Authentication Failed”# Verify credentials
sendEmail -f sender@gmail.com \
-t recipient@example.com \
-s smtp.gmail.com:587 \
-xu sender@gmail.com \
-xp "password" \
-u "Test" \
-m "Test" \
-o tls=yes \
-v
# Gmail requires app-specific password, not account password
# Generate app-specific password in Gmail settingsTLS Connection Errors
섹션 제목: “TLS Connection Errors”# Test TLS connection
openssl s_client -connect smtp.gmail.com:587 -starttls smtp
# Disable certificate validation (not recommended)
sendEmail -f sender@example.com \
-t recipient@example.com \
-s smtp.example.com:587 \
-xu username \
-xp password \
-u "Test" \
-m "Test" \
-o tls=yes \
-o tls-certfile=/dev/null \
-o tls-strict-certs=noPort Connection Issues
섹션 제목: “Port Connection Issues”# Test SMTP port connectivity
nc -zv smtp.gmail.com 587
telnet smtp.gmail.com 587
# Try alternate ports
sendEmail -s smtp.gmail.com:25
sendEmail -s smtp.gmail.com:465 # SSL
sendEmail -s smtp.gmail.com:587 # TLSEncoding Issues
섹션 제목: “Encoding Issues”# Handle non-ASCII characters
sendEmail -f sender@example.com \
-t recipient@example.com \
-s smtp.example.com:587 \
-u "Spécial Chäracters" \
-m "Message with special chars: ñ, é, ü" \
-o message-charset=UTF-8Best Practices
섹션 제목: “Best Practices”Secure Credential Handling
섹션 제목: “Secure Credential Handling”# Use configuration file instead of command line
chmod 600 email.conf
# Protects password from being visible in process list
# Or use environment variables
export SEND_EMAIL_PASSWORD="password"
sendEmail -f sender@example.com \
-t recipient@example.com \
-s smtp.example.com:587 \
-xu username \
-xp "$SEND_EMAIL_PASSWORD" \
-u "Subject" \
-m "Body"Logging and Auditing
섹션 제목: “Logging and Auditing”# Log all email sends
sendEmail -f sender@example.com \
-t recipient@example.com \
-s smtp.example.com:587 \
-u "Subject" \
-m "Body" \
-v >> email_log.txt 2>&1
# Review logs
tail -f email_log.txtRate Limiting
섹션 제목: “Rate Limiting”# Avoid SMTP rate limits with delays
for email in $(cat recipients.txt); do
sendEmail -f sender@example.com \
-t "$email" \
-s smtp.example.com:587 \
-u "Subject" \
-m "Body"
# Wait between sends
sleep 5
doneSecurity and Legal Considerations
섹션 제목: “Security and Legal Considerations”Authorized Testing Only
섹션 제목: “Authorized Testing Only”- Only send authorized emails during authorized assessments
- Ensure written permission before conducting phishing simulations
- Document all email sending activities
- Follow organizational and legal guidelines
Email Spoofing Awareness
섹션 제목: “Email Spoofing Awareness”- Email spoofing is illegal when used maliciously
- Only test in isolated lab environments or with written authorization
- Understand implications of unauthenticated SMTP servers
Compliance Considerations
섹션 제목: “Compliance Considerations”# Include proper disclaimers in security test emails
DISCLAIMER="
---
This email was sent as part of an authorized security assessment.
If you are not the intended recipient, please delete and report to IT.
---"
sendEmail -f assessor@company.com \
-t employee@company.com \
-s smtp.company.com:587 \
-u "Security Awareness Test" \
-m "Test content$DISCLAIMER" \
-o tls=yesAlternatives and Comparison
섹션 제목: “Alternatives and Comparison”| Tool | Purpose | Differences |
|---|---|---|
| sendEmail | Simple SMTP client | Lightweight, Perl-based |
| mail/mailx | System mail utility | Limited features |
| mutt | Email client | Full client with interactivity |
| curl | Transfer tool | Can send via SMTP with —mail-from |
| ssmtp | SMTP client | Minimal, for system notifications |
Additional Resources
섹션 제목: “Additional Resources”- SMTP Protocol and Standards (RFC 5321)
- TLS/SSL Encryption and Certificates
- Email Header Format and Standards
- Phishing Simulation Best Practices
- Email Security and Authentication (SPF, DKIM, DMARC)