diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..723ef36
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+.idea
\ No newline at end of file
diff --git a/sendmail.go b/sendmail.go
index 5f814ea..cfa78b4 100644
--- a/sendmail.go
+++ b/sendmail.go
@@ -45,7 +45,9 @@ func (m *Mail) Send() error {
 	if m.Header == nil {
 		m.Header = make(http.Header)
 	}
-	m.Header.Set("Content-Type", "text/plain; charset=UTF-8")
+	if m.Header.Get("Content-Type") == "" {
+		m.Header.Set("Content-Type",  "text/plain; charset=UTF-8")
+	}
 	m.Header.Set("Subject", mime.QEncoding.Encode("utf-8", m.Subject))
 	m.Header.Set("From", m.From.String())
 	to := make([]string, len(m.To))
diff --git a/sendmail_test.go b/sendmail_test.go
index f4efa54..701af15 100644
--- a/sendmail_test.go
+++ b/sendmail_test.go
@@ -70,3 +70,30 @@ func TestToError(t *testing.T) {
 		t.Errorf("Expected an error because of missing `To` addresses")
 	}
 }
+
+func TestSetsContentTypeHeader(t *testing.T)  {
+	contentTypeHeader := "Content-Type"
+	contentTypeValue := `text/html; charset="UTF-8"`
+
+	sm := Mail{
+		Subject: "Test sets header",
+		From: maddr("Alexander", "me@"),
+		To: []*mail.Address{maddr("Info", "info@")},
+		Header: map[string][]string{},
+	}
+
+	sm.Header.Set(contentTypeHeader, contentTypeValue)
+
+	io.WriteString(&sm.Text, ":)\r\n")
+
+
+	if err := sm.Send(); err != nil {
+		t.Errorf("%v", err)
+	}
+
+	setHeaderValue := sm.Header.Get(contentTypeHeader)
+
+	if  setHeaderValue != contentTypeValue {
+		t.Errorf("Exepected %s == %s, but it equals %s", contentTypeHeader, contentTypeValue, setHeaderValue)
+	}
+}