feat: add cmd/smtp-test for debugging smtp auth and delivery

cmd/smtp-test/go.mod

@@ -0,0 +1,7 @@
+module github.com/therootcompany/golib/smtp-test
+
+go 1.25.4
+
+require golang.org/x/term v0.39.0
+
+require golang.org/x/sys v0.40.0 // indirect

cmd/smtp-test/go.sum

@@ -0,0 +1,4 @@
+golang.org/x/sys v0.40.0 h1:DBZZqJ2Rkml6QMQsZywtnjnnGvHza6BTfYFWY9kjEWQ=
+golang.org/x/sys v0.40.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/term v0.39.0 h1:RclSuaJf32jOqZz74CkPA9qFuVTX7vhLlpfj/IGWlqY=
+golang.org/x/term v0.39.0/go.mod h1:yxzUCTP/U+FzoxfdKmLaA0RV1WgE0VY7hXBwKtY/4ww=

cmd/smtp-test/main.go

@@ -0,0 +1,156 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"net/smtp"
+	"os"
+	"strings"
+
+	"golang.org/x/term"
+)
+
+const (
+	name         = "smtp-test"
+	licenseYear  = "2026"
+	licenseOwner = "AJ ONeal"
+	licenseType  = "CC0-1.0"
+)
+
+// set by GoReleaser via ldflags
+var (
+	version = "0.0.0-dev"
+	commit  = "0000000"
+	date    = "0001-01-01T00:00:00Z"
+)
+
+func printVersion() {
+	if len(commit) > 7 {
+		commit = commit[:7]
+	}
+	fmt.Fprintf(os.Stderr, "%s v%s %s (%s)\n", name, version, commit, date)
+	fmt.Fprintf(os.Stderr, "Copyright (C) %s %s\n", licenseYear, licenseOwner)
+	fmt.Fprintf(os.Stderr, "Licensed under the %s license\n", licenseType)
+}
+
+type CLIConfig struct {
+	showVersion bool
+	user        string
+	from        string
+	to          string
+	host        string // e.g. smtp.mailgun.org:587 or smtp.gmail.com:587
+	subject     string
+	body        string
+}
+
+func main() {
+	cfg := CLIConfig{
+		subject: "smtp-test - connectivity check",
+		body:    "This is a test message from smtp-test.\nIf you received this, SMTP auth + send worked.",
+	}
+
+	mainFlags := flag.NewFlagSet("", flag.ContinueOnError)
+
+	mainFlags.BoolVar(&cfg.showVersion, "version", false, "Print version and exit")
+	mainFlags.StringVar(&cfg.user, "user", os.Getenv("SMTP_USER"), "Auth email e.g. 'you@gmail.com' or set SMTP_USER")
+	mainFlags.StringVar(&cfg.from, "from", os.Getenv("SMTP_FROM"), "Sender email, e.g. 'you@gmail.com' or set SMTP_FROM")
+	mainFlags.StringVar(&cfg.to, "to", os.Getenv("SMTP_TO"), "Recipient email, e.g. 'test@yourdomain.com' or set SMTP_TO")
+	mainFlags.StringVar(&cfg.host, "host", os.Getenv("SMTP_HOST"), "SMTP server + port, e.g. 'smtp.gmail.com:587' or set SMTP_HOST")
+	mainFlags.StringVar(&cfg.subject, "subject", cfg.subject, "Subject line (default: connectivity check)")
+	mainFlags.StringVar(&cfg.body, "body", cfg.body, "Plain text body (default: test message)")
+
+	mainFlags.Usage = func() {
+		printVersion()
+		out := mainFlags.Output()
+		fmt.Fprintf(out, "\n")
+		fmt.Fprintf(out, "USAGE\n")
+		fmt.Fprintf(out, "   smtp-test [options]\n")
+		fmt.Fprintf(out, "   (or provide most values via environment variables)\n\n")
+		mainFlags.PrintDefaults()
+		fmt.Fprintf(out, "\nExamples:\n")
+		fmt.Fprintf(out, "   SMTP_HOST=smtp.mailgun.org:587 SMTP_FROM=you@mg.domain SMTP_TO=you@gmail.com smtp-test\n")
+		fmt.Fprintf(out, "   smtp-test -host smtp.gmail.com:587 -from you@gmail.com -to debug@yourself.com\n")
+	}
+
+	if len(os.Args) > 1 {
+		switch os.Args[1] {
+		case "-V", "version", "-version", "--version":
+			printVersion()
+			return
+		case "help", "-help", "--help":
+			mainFlags.SetOutput(os.Stdout)
+			mainFlags.Usage()
+			return
+		}
+	}
+
+	if err := mainFlags.Parse(os.Args[1:]); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		mainFlags.SetOutput(os.Stderr)
+		mainFlags.Usage()
+		os.Exit(1)
+	}
+
+	if cfg.showVersion {
+		printVersion()
+		return
+	}
+
+	// Required fields
+	if cfg.from == "" || cfg.to == "" || cfg.host == "" {
+		fmt.Fprintln(os.Stderr, "Missing required parameters: --from, --to, --host (or matching env vars)")
+		mainFlags.Usage()
+		os.Exit(1)
+	}
+
+	user := cfg.user                           // usually same as from for plain auth
+	pass, hasPass := os.LookupEnv("SMTP_PASS") // SMTP_PASS to be consistent style with your SMB_PASSWORD
+	if !hasPass {
+		fmt.Fprintf(os.Stderr, "SMTP_PASS is not set → ")
+		fmt.Print("Password: ")
+		password, err := term.ReadPassword(int(os.Stdin.Fd()))
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "failed to read password: %v\n", err)
+			os.Exit(1)
+		}
+		fmt.Fprintf(os.Stderr, "\n")
+		pass = strings.TrimRight(string(password), "\r\n \t")
+	}
+
+	fmt.Printf("Trying to send from %s → %s via %s ...\n", cfg.from, cfg.to, cfg.host)
+
+	trySMTP(cfg.host, cfg.from, user, pass, cfg.to, cfg.subject, cfg.body)
+	fmt.Println("")
+}
+
+func trySMTP(addr, from, username, password, to, subject, body string) {
+	// Most modern SMTP servers expect 587 + STARTTLS (not native 465 SSL)
+	// net/smtp.SendMail automatically attempts STARTTLS when available.
+	auth := smtp.PlainAuth("", username, password, strings.Split(addr, ":")[0])
+
+	// Build minimal RFC-compliant message
+	msg := (fmt.Appendf(
+		[]byte{},
+		"To: %s\r\n"+
+			"From: %s\r\n"+
+			"Subject: %s\r\n"+
+			"\r\n"+
+			"%s\r\n",
+		to, from, subject, body,
+	))
+
+	err := smtp.SendMail(addr, auth, from, []string{to}, msg)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "SMTP error: %v\n", err)
+		// Common helpful hints
+		if strings.Contains(err.Error(), "535") || strings.Contains(err.Error(), "authentication") {
+			fmt.Fprintln(os.Stderr, "→ Check username/password (Gmail may need app password)")
+		}
+		if strings.Contains(err.Error(), "STARTTLS") || strings.Contains(err.Error(), "TLS") {
+			fmt.Fprintln(os.Stderr, "→ Server may require TLS — try port 587 instead of 465, or vice versa")
+		}
+		return
+	}
+
+	fmt.Printf("Success! Email sent:\n%s\n", string(msg))
+}