do not add empty mime parts, fixes #51

bot/command.go

@@ -430,6 +430,10 @@ func (b *Bot) runSend(ctx context.Context) {
 	for _, to := range tos {
 		email := utils.NewEmail(ID, "", " "+ID, subject, from, to, body, htmlBody, nil)
 		data := email.Compose(b.getBotSettings().DKIMPrivateKey())
+		if data == "" {
+			b.SendError(ctx, evt.RoomID, "email body is empty")
+			return
+		}
 		queued, err := b.Sendmail(evt.ID, from, to, data)
 		if queued {
 			b.log.Error("cannot send email: %v", err)

bot/email.go

@@ -180,6 +180,10 @@ func (b *Bot) SendEmailReply(ctx context.Context) {
 	b.log.Debug("send email reply: %+v", meta)
 	email := utils.NewEmail(meta.MessageID, meta.InReplyTo, meta.References, meta.Subject, meta.From, meta.To, body, htmlBody, nil)
 	data := email.Compose(b.getBotSettings().DKIMPrivateKey())
+	if data == "" {
+		b.SendError(ctx, evt.RoomID, "email body is empty")
+		return
+	}
 
 	queued, err := b.Sendmail(evt.ID, meta.From, meta.To, data)
 	if queued {

utils/email.go

@@ -143,13 +143,23 @@ func (e *Email) Content(threadID id.EventID, options *ContentOptions) *event.Con
 
 // Compose converts the email object to a string (to be used for delivery via SMTP) and possibly DKIM-signs it
 func (e *Email) Compose(privkey string) string {
+	textSize := len(e.Text)
+	htmlSize := len(e.HTML)
+	if textSize == 0 && htmlSize == 0 {
+		return ""
+	}
+
 	mail := enmime.Builder().
 		From("", e.From).
 		To("", e.To).
 		Header("Message-Id", e.MessageID).
-		Subject(e.Subject).
-		Text([]byte(e.Text)).
-		HTML([]byte(e.HTML))
+		Subject(e.Subject)
+	if textSize > 0 {
+		mail = mail.Text([]byte(e.Text))
+	}
+	if htmlSize > 0 {
+		mail = mail.HTML([]byte(e.HTML))
+	}
 	if e.InReplyTo != "" {
 		mail = mail.Header("In-Reply-To", e.InReplyTo)
 	}