Email Verifier using Go

This blog post demonstrates building a simple email verification tool using Go. It's a mini-project designed to illustrate the core concepts of email verification and its underlying mechanisms. We won't delve into every detail, but we'll cover enough to provide a solid understanding.

The process begins with verifying the domain extracted from an email address (e.g., google.com).

Setting up your Go project:

Open your terminal and execute the following commands:

<code class="language-bash">1. go mod init github.com/username/email-verifier  // Replace 'username' with your GitHub username.
2. touch main.go</code>

Implementing the Go code (main.go):

The main.go file will contain the core logic. This initial snippet reads domain inputs from the command line:

<code class="language-go">package main

import (
    "bufio"
    "log"
    "net"
    "os"
    "strings"
)

func main() {
    scanner := bufio.NewScanner(os.Stdin)
    for scanner.Scan() {
        verifyDomain(scanner.Text())
    }

    if err := scanner.Err(); err != nil {
        log.Fatal("Error: could not read from input %v\n", err)
    }
}</code>

The verifyDomain function handles the actual verification process. It checks for MX, SPF, and DMARC records:

<code class="language-go">func verifyDomain(domain string) {
    var hasMX, hasSPF, hasDMARC bool
    var spfRecord, dmarcRecord string

    // MX Record Check
    mxRecords, err := net.LookupMX(domain)
    if err != nil {
        log.Printf("Error: could not find MX record for %s due to %v\n", domain, err)
    }
    if len(mxRecords) > 0 {
        hasMX = true
    }

    // SPF Record Check
    txtRecords, err := net.LookupTXT("spf." + domain)
    if err != nil {
        log.Printf("Error: could not find SPF record for %s due to %v\n", domain, err)
    }
    for _, record := range txtRecords {
        if strings.HasPrefix(record, "v=spf1") {
            hasSPF = true
            spfRecord = record
            break
        }
    }

    // DMARC Record Check
    dmarcRecords, err := net.LookupTXT("_dmarc." + domain)
    if err != nil {
        log.Printf("Error: could not find DMARC record for %s due to %v\n", domain, err)
    }
    for _, record := range dmarcRecords {
        if strings.HasPrefix(record, "v=DMARC1") {
            hasDMARC = true
            dmarcRecord = record
            break
        }
    }

    log.Printf("Domain: %v,\n MX: %v,\n SPF:  %v,\n DMARC:  %v,\n SPF Rec: %v,\n DMARC Rec %v,\n\n", domain, hasMX, hasSPF, hasDMARC, spfRecord, dmarcRecord)
}</code>

Explanation of Email Verification Components:

• MX (Mail Exchanger) Record: Identifies the mail servers responsible for accepting email for a domain.
• SPF (Sender Policy Framework) Record: Specifies authorized mail servers to send emails on behalf of a domain. Helps detect spoofing.
• DMARC (Domain-based Message Authentication, Reporting & Conformance): Builds upon SPF and DKIM for enhanced email authentication and reporting. Specifies how to handle emails failing SPF or DKIM checks.

Running the code:

After saving the code, run it from your terminal: go run main.go. Enter domain names (e.g., google.com, example.com) one at a time. The output will show whether MX, SPF, and DMARC records were found.

Example Output:

<code>Domain: google.com,
 MX: true,
 SPF: false,
 DMARC: true,
 SPF Rec: ,
 DMARC Rec v=DMARC1; p=reject; rua=mailto:mailauth-reports@google.com,
</code>

This output indicates that the domain google.com has an MX record and a DMARC record, but the SPF record lookup failed in this example. The results will vary depending on the domain's DNS configuration.

Remember to replace "github.com/username/email-verifier" with your actual GitHub repository information. Connect with me on LinkedIn, GitHub, and Twitter/X for further discussion!

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