diff --git a/RELEASE.md b/RELEASE.md
index b83765a..6e26214 100644
--- a/RELEASE.md
+++ b/RELEASE.md
@@ -1,5 +1,8 @@
 # Changelog
 
+## [1.2.1] - 2025-xx-xx
+- Add debug logging to SMTP.
+
 ## [1.2.0] - 2025-09-04
 - Added support for YmdHis Date and Base64 template functions
 - Improved campaign review details
diff --git a/backend/log/gomail.go b/backend/log/gomail.go
new file mode 100644
index 0000000..42fdbe6
--- /dev/null
+++ b/backend/log/gomail.go
@@ -0,0 +1,54 @@
+package log
+
+import (
+	"fmt"
+
+	"github.com/wneessen/go-mail/log"
+	"go.uber.org/zap"
+)
+
+// GoMailLoggerAdapter adapts zap.SugaredLogger to go-mail's Logger interface
+type GoMailLoggerAdapter struct {
+	logger *zap.SugaredLogger
+}
+
+func (z *GoMailLoggerAdapter) formatLogMessage(l log.Log) string {
+	direction := "CLIENT"
+	if l.Direction == log.DirServerToClient {
+		direction = "SERVER"
+	}
+
+	// format the message with arguments if present
+	msg := l.Format
+	if len(l.Messages) > 0 {
+		// create interface slice for fmt.Sprintf
+		args := make([]interface{}, len(l.Messages))
+		for i, m := range l.Messages {
+			args[i] = m
+		}
+		msg = fmt.Sprintf(l.Format, args...)
+	}
+
+	return fmt.Sprintf("SMTP %s: %s", direction, msg)
+}
+
+func (z *GoMailLoggerAdapter) Debugf(l log.Log) {
+	z.logger.Debug(z.formatLogMessage(l))
+}
+
+func (z *GoMailLoggerAdapter) Infof(l log.Log) {
+	z.logger.Info(z.formatLogMessage(l))
+}
+
+func (z *GoMailLoggerAdapter) Warnf(l log.Log) {
+	z.logger.Warn(z.formatLogMessage(l))
+}
+
+func (z *GoMailLoggerAdapter) Errorf(l log.Log) {
+	z.logger.Error(z.formatLogMessage(l))
+}
+
+// NewGoMailLoggerAdapter creates a new go-mail logger adapter
+func NewGoMailLoggerAdapter(logger *zap.SugaredLogger) *GoMailLoggerAdapter {
+	return &GoMailLoggerAdapter{logger: logger}
+}
diff --git a/backend/service/campaign.go b/backend/service/campaign.go
index a048480..52da103 100644
--- a/backend/service/campaign.go
+++ b/backend/service/campaign.go
@@ -24,6 +24,7 @@ import (
 	"github.com/phishingclub/phishingclub/data"
 	"github.com/phishingclub/phishingclub/database"
 	"github.com/phishingclub/phishingclub/errs"
+	"github.com/phishingclub/phishingclub/log"
 	"github.com/phishingclub/phishingclub/model"
 	"github.com/phishingclub/phishingclub/repository"
 	"github.com/phishingclub/phishingclub/validate"
@@ -2020,6 +2021,8 @@ func (c *Campaign) sendCampaignMessages(
 		// Try CRAM-MD5 first when credentials are provided
 		emailOptionsCRAM5 := append(emailOptions, mail.WithSMTPAuth(mail.SMTPAuthCramMD5))
 		mc, _ = mail.NewClient(smtpHost.String(), emailOptionsCRAM5...)
+		mc.SetLogger(log.NewGoMailLoggerAdapter(c.Logger))
+		mc.SetDebugLog(true)
 		if build.Flags.Production {
 			mc.SetTLSPolicy(mail.TLSMandatory)
 		} else {
@@ -2033,12 +2036,12 @@ func (c *Campaign) sendCampaignMessages(
 			strings.Contains(err.Error(), "538 ") ||
 			strings.Contains(err.Error(), "CRAM-MD5") ||
 			strings.Contains(err.Error(), "authentication failed")) {
-			c.Logger.Warnw("CRAM-MD5 authentication failed, trying PLAIN auth", "error", err)
+			c.Logger.Debugf("CRAM-MD5 authentication failed, trying PLAIN auth", "error", err)
 			emailOptionsBasic := emailOptions
-			if build.Flags.Production {
-				emailOptionsBasic = append(emailOptions, mail.WithSMTPAuth(mail.SMTPAuthPlain))
-			}
+			emailOptionsBasic = append(emailOptions, mail.WithSMTPAuth(mail.SMTPAuthPlain))
 			mc, _ = mail.NewClient(smtpHost.String(), emailOptionsBasic...)
+			mc.SetLogger(log.NewGoMailLoggerAdapter(c.Logger))
+			mc.SetDebugLog(true)
 			if build.Flags.Production {
 				mc.SetTLSPolicy(mail.TLSMandatory)
 			} else {
@@ -2049,6 +2052,8 @@ func (c *Campaign) sendCampaignMessages(
 	} else {
 		// No credentials provided, try without authentication (e.g., local postfix)
 		mc, _ = mail.NewClient(smtpHost.String(), emailOptions...)
+		mc.SetLogger(log.NewGoMailLoggerAdapter(c.Logger))
+		mc.SetDebugLog(true)
 		if build.Flags.Production {
 			mc.SetTLSPolicy(mail.TLSMandatory)
 		} else {
diff --git a/backend/service/smtpConfiguration.go b/backend/service/smtpConfiguration.go
index 4921acb..4d0809c 100644
--- a/backend/service/smtpConfiguration.go
+++ b/backend/service/smtpConfiguration.go
@@ -12,6 +12,7 @@ import (
 	"github.com/phishingclub/phishingclub/build"
 	"github.com/phishingclub/phishingclub/data"
 	"github.com/phishingclub/phishingclub/errs"
+	"github.com/phishingclub/phishingclub/log"
 	"github.com/phishingclub/phishingclub/model"
 	"github.com/phishingclub/phishingclub/repository"
 	"github.com/phishingclub/phishingclub/validate"
@@ -277,13 +278,14 @@ func (s *SMTPConfiguration) SendTestEmail(
 	}
 	// send mail
 	var mc *mail.Client
-
 	// Try different authentication methods based on configuration
 	// If username is provided, use authentication; otherwise try without auth first
 	if un := username.String(); len(un) > 0 {
 		// Try CRAM-MD5 first when credentials are provided
 		emailOptionsCRAM5 := append(emailOptions, mail.WithSMTPAuth(mail.SMTPAuthCramMD5))
 		mc, _ = mail.NewClient(smtpHost.String(), emailOptionsCRAM5...)
+		mc.SetLogger(log.NewGoMailLoggerAdapter(s.Logger))
+		mc.SetDebugLog(true)
 		if build.Flags.Production {
 			mc.SetTLSPolicy(mail.TLSMandatory)
 		} else {
@@ -297,12 +299,12 @@ func (s *SMTPConfiguration) SendTestEmail(
 			strings.Contains(err.Error(), "538 ") ||
 			strings.Contains(err.Error(), "CRAM-MD5") ||
 			strings.Contains(err.Error(), "authentication failed")) {
-			s.Logger.Warnw("CRAM-MD5 authentication failed, trying PLAIN auth", "error", err)
+			s.Logger.Debugf("CRAM-MD5 authentication failed, trying PLAIN auth", "error", err)
 			emailOptionsBasic := emailOptions
-			if build.Flags.Production {
-				emailOptionsBasic = append(emailOptions, mail.WithSMTPAuth(mail.SMTPAuthPlain))
-			}
+			emailOptionsBasic = append(emailOptions, mail.WithSMTPAuth(mail.SMTPAuthPlain))
 			mc, _ = mail.NewClient(smtpHost.String(), emailOptionsBasic...)
+			mc.SetLogger(log.NewGoMailLoggerAdapter(s.Logger))
+			mc.SetDebugLog(true)
 			if build.Flags.Production {
 				mc.SetTLSPolicy(mail.TLSMandatory)
 			} else {
@@ -313,6 +315,8 @@ func (s *SMTPConfiguration) SendTestEmail(
 	} else {
 		// No credentials provided, try without authentication (e.g., local postfix)
 		mc, _ = mail.NewClient(smtpHost.String(), emailOptions...)
+		mc.SetLogger(log.NewGoMailLoggerAdapter(s.Logger))
+		mc.SetDebugLog(true)
 		if build.Flags.Production {
 			mc.SetTLSPolicy(mail.TLSMandatory)
 		} else {