SSL/TLS Receive Mail (POP3)

SSL POP3 Mail Example

Overview

This NetBurner embedded application demonstrates how to retrieve email from a server that requires SSL/TLS using the POP3 protocol. The application provides a web interface for configuring mail server settings and retrieving messages, which are then saved to external flash storage.

Note

When connecting to a Google Account, you will likely need to enable less secure application access. If you use two-factor authentication with your account, you will need to setup an application password for the account being connected to. This can be done at the following URL: https://myaccount.google.com/apppasswords. The application password is not saved and will need to be reentered for every request.

Key Features

• SSL/TLS POP3 Email Retrieval: Secure connection to POP3 mail servers
• Web-based Configuration Interface: HTML forms for setting up mail server credentials
• File System Integration: Saves retrieved emails to SD/MMC/SDHC cards or Compact Flash
• FTP Server: Built-in FTP server for file management
• HTTPS Web Server: Secure web interface on port 443
• Multiple Storage Support: Compatible with various flash storage types

Application Components

Main Application (main.cpp)

The main application initializes:

• Network stack with DHCP support
• File system for multiple task priorities
• External flash storage (SD/MMC/SDHC/CFC)
• HTTPS web server on port 443
• FTP server on port 21

File System Utilities

• FileSystemUtils.cpp/h: Comprehensive file system operations including mount/unmount, format, read/write operations, and directory management
• cardtype.h: Hardware abstraction for different storage types (SD/MMC, SDHC, CFC, RAM)

Network Services

• FTP Server (ftp_f.cpp/h): Full FTP implementation with file transfer, directory operations, and multi-drive support
• Web Interface (webfuncs.cpp): HTTP POST/GET handlers for email configuration and retrieval

Time Management

• effs_time.cpp/h: Time synchronization using NTP servers, manual time setting, and RTC integration for file timestamps

Web Interface

The application provides an HTML-based interface accessible via HTTPS:

Main Page (index.html)

• Network configuration display (IP, gateway, DNS)
• POP3 server settings form:
  • Mail username and password
  • POP3 server hostname/IP
  • Port number (default 995 for SSL)
  • Number of messages to retrieve

Results Page (sent.html)

• Displays retrieval status
• Provides links to downloaded email files
• Shows error details if retrieval fails

Storage Configuration

The application supports multiple storage types configured in cardtype.h:

• SDHC: SD/SDHC cards (default for SB800EX and SOMRT1061 platforms)
• MMC: SD/MMC cards
• CFC: Compact Flash cards
• RAM: RAM-based file system for testing

Gmail Integration Notes

When connecting to Gmail accounts:

1. Enable "Less secure app access" or use App Passwords for 2FA accounts
2. Configure App Password at: https://myaccount.google.com/apppasswords
3. Use server: pop.gmail.com, port: 995
4. The App Password must be re-entered for each session (not stored)

File Operations

Retrieved emails are automatically:

• Converted to HTML format for web viewing
• Saved with sequential filenames (email1.html, email2.html, etc.)
• Accessible via web browser or FTP client
• Timestamped using system time

Error Handling

The application includes comprehensive error handling for:

• Network connectivity issues
• DNS resolution failures
• SSL/TLS connection problems
• File system errors
• Storage device detection and write protection

Build Requirements

• NetBurner development environment
• SSL/TLS library support
• EFFS (Embedded Flash File System) libraries
• Network stack with DHCP and DNS support

Usage Instructions

1. Connect and power the NetBurner device
2. Ensure SD card or other storage is inserted
3. Access the web interface via HTTPS
4. Configure network settings if using static IP
5. Enter POP3 server credentials
6. Click "Get Mail" to retrieve messages
7. Access downloaded emails via provided links or FTP