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# SMTP and IMAP Mail Server |
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A basic SMTP and IMAP server implementation in Rust with TLS/STARTTLS support. |
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## Features |
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### SMTP |
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- ✅ Basic SMTP protocol support (HELO/EHLO, MAIL FROM, RCPT TO, DATA, QUIT) |
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- ✅ STARTTLS support for secure connections |
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- ✅ Self-signed certificate generation for TLS |
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- ✅ Multiple recipient support |
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- ✅ Command validation and error handling |
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- ✅ Dual-mode operation: separate ports for incoming and outgoing mail |
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### IMAP |
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- ✅ IMAP4rev1 protocol implementation |
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- ✅ Essential commands (LOGIN, SELECT, EXAMINE, FETCH, SEARCH, LIST, STATUS, LOGOUT, CAPABILITY) |
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- ✅ Mailbox management (INBOX, Sent, Drafts, Trash) |
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- ✅ Message storage and retrieval |
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- ✅ UID and sequence number support |
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- ✅ Message flags (Seen, Answered, Flagged, Deleted, Draft, Recent) |
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- ✅ Protocol state management |
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### General |
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- ✅ Async/await with Tokio runtime |
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- ✅ Structured logging with tracing |
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- ✅ Shared message storage between SMTP and IMAP |
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## Running the Server |
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```bash |
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cargo run |
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``` |
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The SMTP server listens on two ports: |
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- `127.0.0.1:2525` - **Receive mode**: For incoming mail from other servers (messages stored in INBOX) |
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- `127.0.0.1:2526` - **Submit mode**: For outgoing mail submission from clients (messages logged and relayed) |
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The IMAP server listens on `127.0.0.1:1143` by default. |
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## Testing |
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### Testing SMTP |
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You can test the SMTP server using `nc` (netcat) or `telnet`: |
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**Testing receive mode (port 2525):** |
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```bash |
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echo -e "EHLO test.com\r\nMAIL FROM: <sender@example.com>\r\nRCPT TO: <recipient@example.com>\r\nDATA\r\nSubject: Test\r\n\r\nTest message\r\n.\r\nQUIT\r\n" | nc localhost 2525 |
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``` |
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**Testing submit mode (port 2526):** |
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```bash |
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echo -e "EHLO test.com\r\nMAIL FROM: <sender@example.com>\r\nRCPT TO: <recipient@example.com>\r\nDATA\r\nSubject: Outgoing Test\r\n\r\nOutgoing message\r\n.\r\nQUIT\r\n" | nc localhost 2526 |
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``` |
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### Testing IMAP |
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You can test the IMAP server using `nc` (netcat) or `telnet`: |
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```bash |
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# Connect and login |
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echo -e "a1 CAPABILITY\r\na2 LOGIN user pass\r\na3 LIST \"\" \"*\"\r\na4 SELECT INBOX\r\na5 LOGOUT\r\n" | nc localhost 1143 |
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# Fetch messages |
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echo -e "a1 LOGIN user pass\r\na2 SELECT INBOX\r\na3 FETCH 1 (FLAGS BODY[])\r\na4 LOGOUT\r\n" | nc localhost 1143 |
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``` |
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## Supported Commands |
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### SMTP Commands |
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- `HELO/EHLO` - Initiate SMTP session |
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- `MAIL FROM` - Specify sender email address |
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- `RCPT TO` - Specify recipient email address (supports multiple) |
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- `DATA` - Begin email message content |
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- `RSET` - Reset the current transaction |
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- `NOOP` - No operation (keepalive) |
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- `QUIT` - Close connection |
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- `STARTTLS` - Upgrade connection to TLS |
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### IMAP Commands |
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- `CAPABILITY` - List server capabilities |
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- `LOGIN` - Authenticate user |
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- `LIST/LSUB` - List available mailboxes |
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- `SELECT` - Select a mailbox (read-write) |
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- `EXAMINE` - Select a mailbox (read-only) |
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- `FETCH` - Retrieve message data |
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- `SEARCH` - Search for messages |
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- `STATUS` - Get mailbox status |
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- `LOGOUT` - Close connection |
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- `NOOP` - No operation (keepalive) |
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## Building |
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```bash |
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cargo build --release |
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``` |
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## Dependencies |
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- `tokio` - Async runtime |
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- `anyhow` - Error handling |
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- `tracing` / `tracing-subscriber` - Logging |
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- `regex` - SMTP command parsing |
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- `native-tls` / `tokio-native-tls` - TLS support |
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- `openssl` - Certificate generation |
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- `futures` - Stream handling |
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- `tokio-util` - Codec utilities |