diff --git a/msg_test.go b/msg_test.go
index b09e514..20c44fd 100644
--- a/msg_test.go
+++ b/msg_test.go
@@ -19,6 +19,7 @@ import (
 	"net"
 	"os"
 	"reflect"
+	"runtime"
 	"strings"
 	"testing"
 	ttpl "text/template"
@@ -6056,6 +6057,10 @@ func TestMsg_WriteTo(t *testing.T) {
 		if _, err := message.WriteTo(buffer); err != nil {
 			t.Fatalf("failed to write message to buffer: %s", err)
 		}
+		fileContentType := "text/plain"
+		if runtime.GOOS == "freebsd" {
+			fileContentType = "application/octet-stream"
+		}
 		wants := []msgContentTest{
 			{0, "Date:", false, true, false},
 			{1, "MIME-Version: 1.0", true, true, false},
@@ -6090,7 +6095,7 @@ func TestMsg_WriteTo(t *testing.T) {
 			{32, `Content-Disposition: inline; filename="embed.txt"`, true, true, false},
 			{33, "Content-Id: <embed.txt>", true, true, false},
 			{34, "Content-Transfer-Encoding: base64", true, true, false},
-			{35, `Content-Type: text/plain; charset=utf-8; name="embed.txt"`, true, true, false},
+			{35, `Content-Type: ` + fileContentType + `; charset=utf-8; name="embed.txt"`, true, true, false},
 			{36, "", true, false, false},
 			{37, "VGhp", false, true, false},
 			{38, "", true, false, false},
@@ -6099,7 +6104,7 @@ func TestMsg_WriteTo(t *testing.T) {
 			{41, "--", false, true, false},
 			{42, `Content-Disposition: attachment; filename="attachment.txt"`, true, true, false},
 			{43, "Content-Transfer-Encoding: base64", true, true, false},
-			{44, `Content-Type: text/plain; charset=utf-8; name="attachment.txt"`, true, true, false},
+			{44, `Content-Type: ` + fileContentType + `; charset=utf-8; name="attachment.txt"`, true, true, false},
 			{45, "", true, false, false},
 			{46, "VGhp", false, true, false},
 			{47, "", true, false, false},
@@ -6123,6 +6128,10 @@ func TestMsg_WriteTo(t *testing.T) {
 		if _, err := message.WriteTo(buffer); err != nil {
 			t.Fatalf("failed to write message to buffer: %s", err)
 		}
+		fileContentType := "text/plain"
+		if runtime.GOOS == "freebsd" {
+			fileContentType = "application/octet-stream"
+		}
 		wants := []msgContentTest{
 			{0, "Date:", false, true, false},
 			{1, "MIME-Version: 1.0", true, true, false},
@@ -6164,7 +6173,7 @@ func TestMsg_WriteTo(t *testing.T) {
 			{36, `Content-Disposition: inline; filename="embed.txt"`, true, true, false},
 			{37, "Content-Id: <embed.txt>", true, true, false},
 			{38, "Content-Transfer-Encoding: base64", true, true, false},
-			{39, `Content-Type: text/plain; charset=utf-8; name="embed.txt"`, true, true, false},
+			{39, `Content-Type: ` + fileContentType + `; charset=utf-8; name="embed.txt"`, true, true, false},
 			{40, "", true, false, false},
 			{41, "VGhp", false, true, false},
 			{42, "", true, false, false},
@@ -6173,7 +6182,7 @@ func TestMsg_WriteTo(t *testing.T) {
 			{45, "--", false, true, false},
 			{46, `Content-Disposition: attachment; filename="attachment.txt"`, true, true, false},
 			{47, "Content-Transfer-Encoding: base64", true, true, false},
-			{48, `Content-Type: text/plain; charset=utf-8; name="attachment.txt"`, true, true, false},
+			{48, `Content-Type: ` + fileContentType + `; charset=utf-8; name="attachment.txt"`, true, true, false},
 			{49, "", true, false, false},
 			{50, "VGhp", false, true, false},
 			{51, "", true, false, false},