A bare-minimum TCP-level SMTP server implementation in Go for a server to send and receive emails.

• SMTP server listening on port 25
• Handles basic SMTP commands (HELO/EHLO, MAIL FROM, RCPT TO, DATA)
• Email validation for local domain (@abby.md)
• Support for concurrent connections using goroutines
• MX record lookup
• Custom CRLF scanning for proper SMTP protocol handling

git clone <repository-url>
cd gtsmail
go build

To start the SMTP server:

sudo go run main.go

Note: Running on port 25 requires root/administrator privileges, and ISP restrictions may apply.

The program includes functionality to:

• Look up MX records for recipient domains
• Forward emails to appropriate mail servers
• Handle multiple MX records with priority ordering
• Support timeout and error handling

Run the included tests with:

go test ./...

• main.go - SMTP server implementation
• send.go - Functions to send emails and handle MX records
• send_test.go - Test cases

This project is available under the MIT License.