Added more TLS options to resolve a common issue

README.md

@@ -3,6 +3,7 @@
 </p>
 
 # Mail2Go - Lightweight CLI SMTP client
+
 ![License](https://img.shields.io/github/license/KeepSec-Technologies/Mail2Go)
 ![GitHub issues](https://img.shields.io/github/issues-raw/KeepSec-Technologies/Mail2Go)
 ![GitHub go.mod Go version (branch & subdirectory of monorepo)](https://img.shields.io/github/go-mod/go-version/KeepSec-Technologies/Mail2Go/main)
@@ -26,7 +27,7 @@ Mail2Go is a very lightweight command-line SMTP client written in Go, designed t
 - **Attachments Support**: Attach multiple files of various types to your emails.
 - **HTML and Plain Text**: Supports both HTML and plain text formats for email bodies.
 - **Command Line Interface**: Easy-to-use CLI arguments for configuring and sending emails.
-- **Flexible Configuration**: SMTP server, port, username, and password can be configured through CLI arguments or a JSON configuration file.
+- **Flexible Configuration**: SMTP server, TLS, port, username, and password can be configured through CLI arguments or a JSON configuration file.
 
 ## Requirements
 
@@ -38,13 +39,13 @@ Mail2Go is a very lightweight command-line SMTP client written in Go, designed t
 1. Download the binary with wget:
 
     ```shell
-    wget https://github.com/KeepSec-Technologies/Mail2Go/releases/download/1.1.3/mail2go_linux_amd64_1.1.3.tar.gz
+    wget https://github.com/KeepSec-Technologies/Mail2Go/releases/download/1.1.4/mail2go_linux_amd64_1.1.4.tar.gz
     ```
 
 2. Unpack it with tar
 
     ```shell
-    tar -xf mail2go_linux_amd64_1.1.3.tar.gz
+    tar -xf mail2go_linux_amd64_1.1.4.tar.gz
     ```
 
 3. Move it to your /usr/local/bin/ (Optional):
@@ -55,7 +56,7 @@ Mail2Go is a very lightweight command-line SMTP client written in Go, designed t
 
 ## Building from Source
 
-1. Ensure you have Go installed on your system. You can download Go from [here](https://golang.org/dl/).
+1. Ensure you have Go installed on your system. You can download Go from [here](https://go.dev/dl/).
 2. Clone the repository:
 
     ```shell
@@ -71,66 +72,60 @@ Mail2Go is a very lightweight command-line SMTP client written in Go, designed t
 4. Build the tool:
 
     ```shell
-    CGO_ENABLED=0 go build -a -installsuffix cgo -o mail2go .
+    go build -o mail2go .
     ```
 
 ## Usage
 
 Run the Mail2Go tool with the required arguments:
 
 ```text
- -s, --smtp-server         SMTP server for sending emails
- -p, --smtp-port           SMTP server port (Default: 587)
- -u, --smtp-username       Username for SMTP authentication
- -w, --smtp-password       Password for SMTP authentication
- -f, --from-email          Email address to send from
- -c, --config              Path to the SMTP json config file which replaces the above arguments
- -t, --to-email            Email addresses that will receive the email, comma-separated
- -h, --subject             Subject of the email
- -b, --body                Body of the email
- -af, --attachments        File paths for attachments, comma-separated
- -bf, --body-file          File path for email body
-```
-
-Those arguments would look like this in your CLI:
-
-```shell
-./mail2go --smtp-server [SMTP_SERVER] --smtp-port [SMTP_PORT] --smtp-username [USERNAME] --smtp-password [PASSWORD] --from-email [FROM_EMAIL] --to-email [TO_EMAIL_1],[TO_EMAIL_2] --subject "Your Subject" --body "Your email body." --attachments "path/to/attachment1,path/to/attachment2"
-```
-
-or
-
-```shell
-./mail2go --config "path/to/config.json" --to-email [TO_EMAIL_1],[TO_EMAIL_2] --subject "Your Subject" --body-file "path/to/email.html" --attachments "path/to/attachment1,path/to/attachment2"
+-s, --smtp-server         SMTP server for sending emails
+-p, --smtp-port           SMTP server port (Default: 587)
+-u, --smtp-username       Username for SMTP authentication
+-w, --smtp-password       Password for SMTP authentication
+-l, --tls-mode            TLS mode (none, tls-skip, tls)
+-f, --from-email          Email address to send from
+
+-c, --config              Path to the SMTP json config file which replaces the above arguments
+
+-t, --to-email            Email addresses that will receive the email, can be multiples (comma-separated)
+-h, --subject             Subject of the email
+-b, --body                Body of the email
+-af, --attachments        File paths for attachments, comma-separated
+-bf, --body-file          File path for email body
 ```
 
 ## Examples
 
-Basic example:
-
 ```shell
-./mail2go -s mail.example.com -u [email protected] -w password123 -f [email protected] -t [email protected] -h 'Test Mail2Go Subject' -b 'This is a body!' 
-```
+# Basic example:
+./mail2go -s mail.example.com -p 587 -u [email protected] -w password123 -l tls -f [email protected] -t [email protected] -h 'Test Mail2Go Subject' -b 'This is a body!' 
 
-Example with two recipients, the body from an HTML file and two attached files (can be more):
+# Example with two recipients, the body from an HTML file and two attached files (can be more):
+./mail2go -s mail.example.com -p 587  -u [email protected] -w password123 -l tls -f [email protected] -t [email protected],[email protected] -h 'Test Mail2Go Subject' -bf demo/body.html -af README.md,demo/mail2go-smaller.png
 
-```shell
-./mail2go -s mail.example.com -u [email protected] -w password123 -f [email protected] -t [email protected],[email protected] -h 'Test Mail2Go Subject' -bf demo/body.html -af README.md,demo/mail2go-smaller.png
+# Example without authentication and no TLS:
+./mail2go -s mail.example.com -p 25 -l none -f [email protected] -t [email protected] -h 'Test Mail2Go Subject' -b 'This is a body!' 
+
+# Example of a local SMTP server with a TLS certificate that can't be verified:
+./mail2go -s localhost -p 587 -u [email protected] -w password123 -l tls-skip -f [email protected] -t [email protected] -h 'Test Mail2Go Subject' -b 'This is a body!' 
 ```
 
-Example of json config file to pass to Mail2Go:
+Example of json configuration file to pass to Mail2Go:
 
 ```json
 {
     "smtp_server": "mail.example.com",
     "smtp_port": 587,
     "smtp_username": "[email protected]",
-    "smtp_password": "password123",
+    "smtp_password": "password_example",
+    "tls_mode": "tls",
     "from_email": "[email protected]"
 }
 ```
 
-The command that goes with it:
+Example of the command that goes with it:
 
 ```shell
 ./mail2go -c demo/config.json -t [email protected] -h 'Test Mail2Go Subject' -b 'This is a body!' 

config.go

@@ -11,6 +11,7 @@ type Config struct {
 	SMTPPort     int    `json:"smtp_port"`
 	SMTPUsername string `json:"smtp_username"`
 	SMTPPassword string `json:"smtp_password"`
+	TLSMode      string `json:"tls_mode"`
 	FromEmail    string `json:"from_email"`
 }
 

demo/config.json

@@ -2,6 +2,7 @@
     "smtp_server": "mail.example.com",
     "smtp_port": 587,
     "smtp_username": "[email protected]",
-    "smtp_password": "password123",
+    "smtp_password": "password_example",
+    "tls_mode": "tls",
     "from_email": "[email protected]"
 }

demo/postfix/Dockerfile

@@ -0,0 +1,34 @@
+# Use an official Debian image as a parent image
+FROM debian:12
+
+# Set noninteractive installation to avoid prompts
+ENV DEBIAN_FRONTEND=noninteractive
+
+# Install Postfix
+RUN apt-get update && apt-get install -y postfix
+
+# Copy your TLS certificates into the container
+COPY smtp.crt /etc/ssl/certs/smtp.crt
+COPY smtp.key /etc/ssl/private/smtp.key
+
+# Setup Postfix configuration
+RUN postconf -e "myhostname = mydomain.com" \
+    && postconf -e "smtpd_tls_cert_file = /etc/ssl/certs/smtp.crt" \
+    && postconf -e "smtpd_tls_key_file = /etc/ssl/private/smtp.key" \
+    && postconf -e "smtpd_tls_security_level = may" \
+    && postconf -e "smtpd_tls_auth_only = no" \
+    && postconf -e "smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination" \
+    && postconf -e "mydestination = $myhostname, localhost.$mydomain, localhost" \
+    && postconf -e "mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 0.0.0.0/0" \
+    && postconf -e "inet_interfaces = all" \
+    && postconf -e "inet_protocols = ipv4" \
+    && postconf -e "smtpd_recipient_restrictions = permit_mynetworks permit_sasl_authenticated reject_unauth_destination" \
+    && postconf -e "smtp_bind_address = 0.0.0.0" \
+    && postconf -e "smtpd_sasl_auth_enable = no"
+
+# Expose ports for SMTP
+EXPOSE 25
+
+# Start Postfix
+CMD ["postfix", "start-fg"]
+

demo/postfix/smtp.crt

@@ -0,0 +1,22 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----

demo/postfix/smtp.key

@@ -0,0 +1,28 @@
+-----BEGIN PRIVATE KEY-----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+-----END PRIVATE KEY-----

main.go

@@ -3,7 +3,6 @@ package main
 import (
 	"flag"
 	"fmt"
-	"log"
 	"os"
 	"strings"
 )
@@ -15,6 +14,8 @@ var (
 	username   string
 	password   string
 
+	tlsMode string
+
 	configFile string
 
 	fromEmail string
@@ -32,6 +33,8 @@ var (
 	usernameShort   string
 	passwordShort   string
 
+	tlsModeShort string
+
 	configFileShort string
 
 	fromEmailShort string
@@ -51,6 +54,8 @@ func init() {
 	flag.StringVar(&username, "smtp-username", "", "Username for SMTP authentication")
 	flag.StringVar(&password, "smtp-password", "", "Password for SMTP authentication")
 
+	flag.StringVar(&tlsMode, "tls-mode", "", "TLS mode (none, tls-skip, tls)")
+
 	flag.StringVar(&configFile, "config", "", "Path to the SMTP config file")
 
 	flag.StringVar(&fromEmail, "from-email", "", "Email address to send from")
@@ -68,6 +73,8 @@ func init() {
 	flag.StringVar(&usernameShort, "u", "", "Username for SMTP authentication (short)")
 	flag.StringVar(&passwordShort, "w", "", "Password for SMTP authentication (short)")
 
+	flag.StringVar(&tlsModeShort, "l", "", "TLS mode (short)")
+
 	flag.StringVar(&configFileShort, "c", "", "Path to the SMTP config file (short)")
 
 	flag.StringVar(&fromEmailShort, "f", "", "Email address to send from (short)")
@@ -81,6 +88,8 @@ func init() {
 }
 
 func main() {
+	// Override the default flag.Usage
+	flag.Usage = Usage
 	flag.Parse()
 
 	// Override long-form flags with short-form flags if set
@@ -96,6 +105,9 @@ func main() {
 	if passwordShort != "" {
 		password = passwordShort
 	}
+	if tlsModeShort != "" {
+		tlsMode = tlsModeShort
+	}
 	if configFileShort != "" {
 		configFile = configFileShort
 	}
@@ -122,7 +134,7 @@ func main() {
 	if configFile != "" {
 		config, err := loadConfig(configFile)
 		if err != nil {
-			log.Fatalf("Error loading config file: %v", err)
+			fmt.Printf("Error loading config file: %v", err)
 		}
 
 		// Override flags with config file values if set
@@ -138,28 +150,31 @@ func main() {
 		if config.SMTPPassword != "" {
 			password = config.SMTPPassword
 		}
+		if config.TLSMode != "" {
+			tlsMode = config.TLSMode
+		}
 		if config.FromEmail != "" {
 			fromEmail = config.FromEmail
 		}
 	}
 
 	// Check if required flags or config values are missing
-	if smtpServer == "" || username == "" || password == "" || fromEmail == "" || toEmail == "" || subject == "" {
+	if smtpServer == "" || tlsMode == "" || fromEmail == "" || toEmail == "" || subject == "" {
 		fmt.Fprintln(os.Stderr, "Error: Required flags or config values are missing.")
-		usage()
+		Usage()
 	}
 
 	// Check if either direct input or file path is provided for body
 	if body == "" && bodyFile == "" {
 		fmt.Fprintln(os.Stderr, "Error: Subject and body are required, either directly or through a specified file.")
-		usage()
+		Usage()
 	}
 
 	// Read body from files if provided
 	if bodyFile != "" {
 		content, err := os.ReadFile(bodyFile)
 		if err != nil {
-			log.Fatalf("\nError reading body file: %v\n", err)
+			fmt.Printf("\nError reading body file: %v\n", err)
 		}
 		body = string(content)
 	}
@@ -178,8 +193,8 @@ func main() {
 
 	if len(toEmails) == 0 {
 		fmt.Fprintln(os.Stderr, "Error: At least one recipient email address is required.")
-		usage()
+		Usage()
 	}
 
-	sendEmail(smtpServer, smtpPort, username, password, fromEmail, toEmails, subject, body, bodyFile, attachmentPaths)
+	sendEmail(smtpServer, smtpPort, username, password, fromEmail, toEmails, subject, body, bodyFile, attachmentPaths, tlsMode)
 }