diff --git a/curves.go b/curves.go
new file mode 100644
index 0000000..e72c310
--- /dev/null
+++ b/curves.go
@@ -0,0 +1,14 @@
+//go:build !go1.24
+
+package main
+
+import (
+	"crypto/tls"
+)
+
+var curvesList = []tls.CurveID{
+	tls.CurveP256,
+	tls.CurveP384,
+	tls.CurveP521,
+	tls.X25519,
+}
diff --git a/curves_go124.go b/curves_go124.go
new file mode 100644
index 0000000..424886b
--- /dev/null
+++ b/curves_go124.go
@@ -0,0 +1,15 @@
+//go:build go1.24
+
+package main
+
+import (
+	"crypto/tls"
+)
+
+var curvesList = []tls.CurveID{
+	tls.CurveP256,
+	tls.CurveP384,
+	tls.CurveP521,
+	tls.X25519,
+	tls.X25519MLKEM768,
+}
diff --git a/main.go b/main.go
index 33672bc..b47f846 100644
--- a/main.go
+++ b/main.go
@@ -1921,13 +1921,6 @@ func cmdSMTPDial(c *cmd) {
 		}
 	}
 
-	curvesList := []tls.CurveID{
-		tls.CurveP256,
-		tls.CurveP384,
-		tls.CurveP521,
-		tls.X25519,
-		tls.X25519MLKEM768,
-	}
 	curves := map[string]tls.CurveID{}
 	for _, a := range curvesList {
 		curves[strings.ToLower(a.String())] = a
@@ -2017,7 +2010,7 @@ exchanged during connection set up.
 		tlsConfig.RootCAs = pool
 	}
 	if tlsCiphersuites != "" {
-		for s := range strings.SplitSeq(tlsCiphersuites, ",") {
+		for _, s := range strings.Split(tlsCiphersuites, ",") {
 			s = strings.TrimSpace(s)
 			c, ok := ciphersuites[s]
 			if !ok {
@@ -2030,7 +2023,7 @@ exchanged during connection set up.
 		}
 	}
 	if tlsCurves != "" {
-		for s := range strings.SplitSeq(tlsCurves, ",") {
+		for _, s := range strings.Split(tlsCurves, ",") {
 			s = strings.TrimSpace(s)
 			if c, ok := curves[s]; !ok {
 				log.Fatalf("unknown ecc key exchange algorithm %q", s)