diff --git a/pkg/message/header.go b/pkg/message/header.go
index fe08f1d2..81569a9f 100644
--- a/pkg/message/header.go
+++ b/pkg/message/header.go
@@ -101,12 +101,6 @@ func GetBodyHeader(m *pmapi.Message) textproto.MIMEHeader {
 	return h
 }
 
-func GetRelatedHeader(m *pmapi.Message) textproto.MIMEHeader {
-	h := make(textproto.MIMEHeader)
-	h.Set("Content-Type", "multipart/related; boundary="+GetRelatedBoundary(m))
-	return h
-}
-
 func GetAttachmentHeader(att *pmapi.Attachment, buildForIMAP bool) textproto.MIMEHeader {
 	mediaType := att.MIMEType
 	if mediaType == "application/pgp-encrypted" {
diff --git a/pkg/message/message.go b/pkg/message/message.go
index 90ab4930..1652f67b 100644
--- a/pkg/message/message.go
+++ b/pkg/message/message.go
@@ -38,12 +38,6 @@ func GetBoundary(m *pmapi.Message) string {
 	return fmt.Sprintf("%x", sha512.Sum512_256([]byte(m.ID)))
 }
 
-func GetRelatedBoundary(m *pmapi.Message) string {
-	// The boundary needs to be deterministic because messages are not supposed to
-	// change.
-	return fmt.Sprintf("%x", sha512.Sum512_256([]byte(m.ID+m.ID)))
-}
-
 func SeparateInlineAttachments(m *pmapi.Message) (atts, inlines []*pmapi.Attachment) {
 	for _, att := range m.Attachments {
 		if strings.Contains(att.Header.Get("Content-Disposition"), pmapi.DispositionInline) {