diff --git a/server.go b/server.go
index eacdba3..4185957 100644
--- a/server.go
+++ b/server.go
@@ -17,6 +17,7 @@ import (
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/codes"
 	tracesdk "go.opentelemetry.io/otel/sdk/trace"
+	semconv "go.opentelemetry.io/otel/semconv/v1.21.0"
 	"go.opentelemetry.io/otel/trace"
 )
 
@@ -139,7 +140,8 @@ type Server struct {
 	EnableXCLIENT bool
 	// EnableProxyProtocol enables Proxy command support (disabled by default, since it is security risk)
 	EnableProxyProtocol bool
-
+	// HideTransactionHeader hides transaction header
+	HideTransactionHeader bool
 	// TLSConfig is used both for STARTTLS and operation over TLS channel
 	TLSConfig *tls.Config
 	// ForceTLS requires connections to be encrypted
@@ -186,9 +188,8 @@ func (srv *Server) startTransaction(c net.Conn) (t *Transaction) {
 	remoteAddr := c.RemoteAddr().(*net.TCPAddr)
 	ctxWithTracer, span := srv.Tracer.Start(ctx, "transaction",
 		trace.WithSpanKind(trace.SpanKindServer), // важно
-		trace.WithAttributes(attribute.String("remote_addr", c.RemoteAddr().String())),
-		trace.WithAttributes(attribute.String("remote_ip", remoteAddr.IP.String())),
-		trace.WithAttributes(attribute.Int("remote_port", remoteAddr.Port)),
+		trace.WithAttributes(semconv.ClientSocketAddress(remoteAddr.IP.String())),
+		trace.WithAttributes(semconv.ClientSocketPort(remoteAddr.Port)),
 	)
 	t = &Transaction{
 		ID:        span.SpanContext().TraceID().String(),
diff --git a/server_counters_test.go b/server_counters_test.go
index 91b00da..bd73850 100644
--- a/server_counters_test.go
+++ b/server_counters_test.go
@@ -75,7 +75,7 @@ func TestCounters(t *testing.T) {
 	if srv.lastTransactionStartedAt.IsZero() {
 		t.Errorf("transaction time is not set")
 	}
-	if time.Now().Sub(srv.lastTransactionStartedAt) > 3*time.Second {
+	if time.Since(srv.lastTransactionStartedAt) > 3*time.Second {
 		t.Errorf("last transaction time is too old")
 	}
 }
diff --git a/transaction_auth.go b/transaction_auth.go
index 1b6492a..b286f89 100644
--- a/transaction_auth.go
+++ b/transaction_auth.go
@@ -6,6 +6,7 @@ import (
 	"strings"
 
 	"go.opentelemetry.io/otel/attribute"
+	semconv "go.opentelemetry.io/otel/semconv/v1.21.0"
 )
 
 func (t *Transaction) handleAUTH(cmd command) {
@@ -58,7 +59,7 @@ func (t *Transaction) handleAUTH(cmd command) {
 		}
 		username = string(parts[1])
 		password = string(parts[2])
-		break
+
 	case "LOGIN":
 		encodedUsername := ""
 		if len(cmd.fields) < 3 {
@@ -87,7 +88,7 @@ func (t *Transaction) handleAUTH(cmd command) {
 		}
 		username = string(byteUsername)
 		password = string(bytePassword)
-		break
+
 	default:
 		t.LogDebug("unknown authentication mechanism: %s", mechanism)
 		t.reply(502, "Unknown authentication mechanism")
@@ -106,8 +107,7 @@ func (t *Transaction) handleAUTH(cmd command) {
 	// i know saving password here is security risk, but we can implement something like
 	// Haraka plugin to prevent credential leaks
 	// https://haraka.github.io/plugins/prevent_credential_leaks
-	t.Span.SetAttributes(attribute.String("username", username))
-	t.Span.SetAttributes(attribute.String("password", mask(password)))
+	t.Span.SetAttributes(semconv.EnduserID(username))
+	t.Span.SetAttributes(attribute.String("enduser.password", mask(password)))
 	t.reply(235, "OK, you are now authenticated")
-	return
 }
diff --git a/transaction_data.go b/transaction_data.go
index c418f7f..58a94c1 100644
--- a/transaction_data.go
+++ b/transaction_data.go
@@ -31,7 +31,7 @@ var uniqueHeaders = []string{
 	"Subject",
 }
 
-func (t *Transaction) handleDATA(cmd command) {
+func (t *Transaction) handleDATA(_ command) {
 	var checkErr error
 	var deliverErr error
 	var createdAt time.Time
@@ -69,15 +69,21 @@ func (t *Transaction) handleDATA(cmd command) {
 	}
 	t.LogDebug("DATA is called...")
 	t.reply(354, "Ok, you managed to talk me into accepting your message. Go on, end your data with <CR><LF>.<CR><LF>")
-	t.conn.SetDeadline(time.Now().Add(t.server.DataTimeout))
+	err := t.conn.SetDeadline(time.Now().Add(t.server.DataTimeout))
+	if err != nil {
+		t.LogError(err, "while setting deadline for connection")
+		return
+	}
 	data := bytes.NewBufferString("")
 	reader := textproto.NewReader(t.reader).DotReader()
-	_, err := io.CopyN(data, reader, int64(t.server.MaxMessageSize))
+	_, err = io.CopyN(data, reader, int64(t.server.MaxMessageSize))
 	if err != nil {
 		if err == io.EOF {
 			// EOF was reached before MaxMessageSize, so we can accept and deliver message
 			t.Body = data.Bytes()
-			t.AddHeader("MSMTPD-Transaction-Id", t.ID)
+			if !t.server.HideTransactionHeader {
+				t.AddHeader("MSMTPD-Transaction-Id", t.ID)
+			}
 			t.AddReceivedLine() // will be added as first one
 			t.LogDebug("Parsing message body with size %v...", data.Len())
 			t.Span.SetAttributes(attribute.Int("size", data.Len()))
@@ -205,5 +211,4 @@ func (t *Transaction) handleDATA(cmd command) {
 	))
 	t.Hate(tooBigMessagePenalty)
 	t.reset()
-	return
 }
diff --git a/transaction_handler.go b/transaction_handler.go
index 1635316..1767365 100644
--- a/transaction_handler.go
+++ b/transaction_handler.go
@@ -12,40 +12,28 @@ func (t *Transaction) handle(line string) {
 	switch cmd.action {
 	case "PROXY":
 		t.handlePROXY(cmd)
-		break
 	case "HELO":
 		t.handleHELO(cmd)
-		break
 	case "EHLO":
 		t.handleEHLO(cmd)
-		break
 	case "MAIL":
 		t.handleMAIL(cmd)
-		break
 	case "RCPT":
 		t.handleRCPT(cmd)
-		break
 	case "STARTTLS":
 		t.handleSTARTTLS(cmd)
-		break
 	case "DATA":
 		t.handleDATA(cmd)
-		break
 	case "RSET":
 		t.handleRSET(cmd)
-		break
 	case "NOOP":
 		t.handleNOOP(cmd)
-		break
 	case "QUIT":
 		t.handleQUIT(cmd)
-		break
 	case "AUTH":
 		t.handleAUTH(cmd)
-		break
 	case "XCLIENT":
 		t.handleXCLIENT(cmd)
-		break
 	default:
 		t.Hate(unknownCommandPenalty)
 		t.LogDebug("Unsupported command received: %s", line)
@@ -53,19 +41,16 @@ func (t *Transaction) handle(line string) {
 	}
 }
 
-func (t *Transaction) handleRSET(cmd command) {
+func (t *Transaction) handleRSET(_ command) {
 	t.reset()
 	t.reply(250, "I forgot everything you have said, go ahead please!")
-	return
 }
 
-func (t *Transaction) handleNOOP(cmd command) {
+func (t *Transaction) handleNOOP(_ command) {
 	t.reply(250, "I'm finishing procrastinating, go ahead please!")
-	return
 }
 
-func (t *Transaction) handleQUIT(cmd command) {
+func (t *Transaction) handleQUIT(_ command) {
 	t.reply(221, fmt.Sprintf("Farewell, my friend! Transaction %s is finished", t.ID))
 	t.close()
-	return
 }
diff --git a/transaction_helo.go b/transaction_helo.go
index a3f0d49..dfe6bc0 100644
--- a/transaction_helo.go
+++ b/transaction_helo.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"go.opentelemetry.io/otel/attribute"
+	semconv "go.opentelemetry.io/otel/semconv/v1.21.0"
 )
 
 func (t *Transaction) handleHELO(cmd command) {
@@ -21,7 +22,7 @@ func (t *Transaction) handleHELO(cmd command) {
 	t.HeloName = cmd.fields[1]
 	t.Protocol = SMTP
 	t.Span.SetAttributes(attribute.String("helo", t.HeloName))
-	t.Span.SetAttributes(attribute.String("protocol", "SMTP"))
+	t.Span.SetAttributes(semconv.NetProtocolName("smtp"))
 	for k := range t.server.HeloCheckers {
 		err = t.server.HeloCheckers[k](t)
 		if err != nil {
@@ -68,7 +69,7 @@ func (t *Transaction) handleEHLO(cmd command) {
 	t.HeloName = cmd.fields[1]
 	t.Protocol = ESMTP
 	t.Span.SetAttributes(attribute.String("ehlo", t.HeloName))
-	t.Span.SetAttributes(attribute.String("protocol", "ESMTP"))
+	t.Span.SetAttributes(semconv.NetProtocolName("esmtp"))
 	for k := range t.server.HeloCheckers {
 		err = t.server.HeloCheckers[k](t)
 		if err != nil {
diff --git a/transaction_mailfrom.go b/transaction_mailfrom.go
index 28770e9..6643520 100644
--- a/transaction_mailfrom.go
+++ b/transaction_mailfrom.go
@@ -66,5 +66,4 @@ func (t *Transaction) handleMAIL(cmd command) {
 	)
 	t.reply(250, "Ok, it makes sense, go ahead please!")
 	t.Love(commandExecutedProperly)
-	return
 }
diff --git a/transaction_proxy.go b/transaction_proxy.go
index a54593f..de56b37 100644
--- a/transaction_proxy.go
+++ b/transaction_proxy.go
@@ -22,8 +22,8 @@ func (t *Transaction) handlePROXY(cmd command) {
 		return
 	}
 	var (
-		newAddr    net.IP = nil
-		newTCPPort uint64 = 0
+		newAddr    net.IP
+		newTCPPort uint64
 		err        error
 	)
 	switch cmd.fields[1] {
diff --git a/transaction_rcpt_to.go b/transaction_rcpt_to.go
index cb2ebae..9d85ee9 100644
--- a/transaction_rcpt_to.go
+++ b/transaction_rcpt_to.go
@@ -62,13 +62,10 @@ func (t *Transaction) handleRCPT(cmd command) {
 	switch len(t.RcptTo) {
 	case 1:
 		t.LogInfo("Recipient %s will be 1st one in transaction!", addr)
-		break
 	case 2:
 		t.LogInfo("Recipient %s will be 2nd one in transaction!", addr)
-		break
 	case 3:
 		t.LogInfo("Recipient %s will be 3rd one in transaction!", addr)
-		break
 	default:
 		t.LogInfo("Recipient %s will be %dth one in transaction!", addr, len(t.RcptTo))
 	}
@@ -86,5 +83,4 @@ func (t *Transaction) handleRCPT(cmd command) {
 	if len(t.RcptTo) == 1 { // too many recipients should not give too many love for transaction
 		t.Love(commandExecutedProperly)
 	}
-	return
 }
diff --git a/transaction_startTLS.go b/transaction_startTLS.go
index 9a8500b..fa6c4c5 100644
--- a/transaction_startTLS.go
+++ b/transaction_startTLS.go
@@ -9,6 +9,7 @@ import (
 )
 
 func (t *Transaction) handleSTARTTLS(cmd command) {
+	var err error
 	if t.Encrypted {
 		t.LogDebug("Connection is already encrypted!")
 		t.reply(502, "Already running in TLS")
@@ -21,7 +22,8 @@ func (t *Transaction) handleSTARTTLS(cmd command) {
 	t.LogDebug("STARTTLS [%s] is received...", cmd.line)
 	tlsConn := tls.Server(t.conn, t.server.TLSConfig)
 	t.reply(220, "Connection is encrypted, we can talk freely now!")
-	if err := tlsConn.Handshake(); err != nil {
+	err = tlsConn.Handshake()
+	if err != nil {
 		t.LogError(err, "couldn't perform handshake")
 		t.reply(550, "TLS Handshake error")
 		return
@@ -32,7 +34,13 @@ func (t *Transaction) handleSTARTTLS(cmd command) {
 	t.reset()
 	// Reset deadlines on the underlying connection before I replace it
 	// with a TLS connection
-	t.conn.SetDeadline(time.Time{})
+	err = t.conn.SetDeadline(time.Time{})
+	if err != nil {
+		t.LogError(err, "error setting deadline for encrypted connection")
+		t.reply(550, "TLS Handshake error")
+		return
+	}
+
 	// Replace connection with a TLS connection
 	t.conn = tlsConn
 	t.reader = bufio.NewReader(tlsConn)
diff --git a/transaction_test.go b/transaction_test.go
index 5895f5e..e2c536f 100644
--- a/transaction_test.go
+++ b/transaction_test.go
@@ -61,7 +61,7 @@ func TestKarma(t *testing.T) {
 	if err != nil {
 		t.Errorf("Data failed: %v", err)
 	}
-	_, err = fmt.Fprintf(wc, internal.MakeTestMessage("sender@example.org", "recipient@example.net"))
+	_, err = fmt.Fprint(wc, internal.MakeTestMessage("sender@example.org", "recipient@example.net"))
 	if err != nil {
 		t.Errorf("Data body failed: %v", err)
 	}
diff --git a/transaction_xclient.go b/transaction_xclient.go
index 73c28fd..acd5b0d 100644
--- a/transaction_xclient.go
+++ b/transaction_xclient.go
@@ -54,9 +54,9 @@ func (t *Transaction) handleXCLIENT(cmd command) {
 			newUsername = value
 			continue
 		case "PROTO":
-			if value == "SMTP" {
+			if value == string(SMTP) {
 				newProto = SMTP
-			} else if value == "ESMTP" {
+			} else if value == string(ESMTP) {
 				newProto = ESMTP
 			}
 			continue