check for sender mailer-daemon as link2xt proposed

src/imap/mod.rs

@@ -1458,7 +1458,7 @@ pub(crate) async fn prefetch_should_download(
     let is_reply_to_chat_message = prefetch_is_reply_to_chat_message(context, &headers).await;
 
     let maybe_ndn = if let Some(from) = headers.get_header_value(HeaderDef::From_) {
-        from.to_ascii_lowercase().contains("daemon")
+        from.to_ascii_lowercase().contains("mailer-daemon")
     } else {
         false
     };

src/mimeparser.rs

@@ -911,7 +911,7 @@ impl MimeMessage {
             && self
                 .get(HeaderDef::From_)?
                 .to_ascii_lowercase()
-                .contains("daemon")
+                .contains("mailer-daemon")
             && self.failure_report.is_none()
         {
             lazy_static! {