This architecture allows BastionGuard to add an additional security layer to outgoing email traffic **without modifying the behavior of email clients and without requiring integration with email providers**.

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# Key Features

### Local SMTP Proxy
– Transparent SMTP interception for outgoing email.
– Compatible with common mail clients (Thunderbird, Evolution, KMail, Geary, etc.).
– Runs as a lightweight **systemd user service**.
– No client plugins required.

### Multi-SMTP Relay Support
– Multiple SMTP relay profiles.
– Profile selection based on sender email or domain.
– Support for multiple providers simultaneously.
– Suitable for personal, corporate, and mixed email environments.

### Antivirus Scanning
– Integration with **ClamAV (clamd)**.
– Scans message body and attachments before sending.
– Uses socket streaming instead of spawning external processes.
– Blocks messages containing malware.

### Anti-Phishing Protection
– Extracts and analyzes URLs in email content.
– Uses BastionGuard’s **AntiPhishingEngine**.
– Detects suspicious or malicious domains before delivery.

### Automatic HTML Signature Injection
– Optional automatic insertion of HTML email signatures.
– Configurable fields:
– name
– job title
– company
– phone
– website
– logo

### Transparent Client Integration
– Works with any SMTP-compatible email client.
– Requires only changing the SMTP server to `127.0.0.1:2525`.
– No modification of the email client software.

### Security Enforcement
– Prevents delivery of malicious emails.
– Provides immediate SMTP feedback to the client.
– Protects both the sender and recipients from infected or phishing emails.

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This feature enables BastionGuard to extend its protection model from **file, network, and browser security to outgoing email traffic**, providing a comprehensive security layer directly at the SMTP level.