diff --git a/deltachat-ffi/deltachat.h b/deltachat-ffi/deltachat.h
index 9a84c85f7..959b44d05 100644
--- a/deltachat-ffi/deltachat.h
+++ b/deltachat-ffi/deltachat.h
@@ -4428,7 +4428,7 @@ void dc_event_unref(dc_event_t* event);
 #define DC_STR_WELCOME_MESSAGE            71
 #define DC_STR_UNKNOWN_SENDER_FOR_CHAT    72
 #define DC_STR_SUBJECT_FOR_NEW_CONTACT    73
-#define FAILED_SENDING_TO                 74
+#define DC_STR_FAILED_SENDING_TO          74
 
 #define DC_STR_COUNT                      74
 
diff --git a/src/message.rs b/src/message.rs
index ad6d5027b..c54c21462 100644
--- a/src/message.rs
+++ b/src/message.rs
@@ -769,7 +769,7 @@ impl MessageState {
             MessageState::OutPreparing
             | MessageState::OutPending
             | MessageState::OutDelivered
-            | MessageState::OutMdnRcvd => true,
+            | MessageState::OutMdnRcvd => true, // OutMdnRcvd can still fail because it could be a group message and only some recipients failed.
             _ => false,
         }
     }
@@ -1328,7 +1328,10 @@ pub async fn mdn_from_ext(
     if let Ok((msg_id, chat_id, chat_type, msg_state)) = res {
         let mut read_by_all = false;
 
-        if msg_state != MessageState::OutMdnRcvd && msg_state != MessageState::OutFailed {
+        if msg_state == MessageState::OutPreparing
+            || msg_state == MessageState::OutPending
+            || msg_state == MessageState::OutDelivered
+        {
             let mdn_already_in_table = context
                 .sql
                 .exists(
@@ -1391,6 +1394,8 @@ pub async fn mdn_from_ext(
     None
 }
 
+/// Marks a message as failed after an ndn (non-delivery-notification) arrived.
+/// Where appropriate, also adds an info message telling the user which of the recipients of a group message failed.
 pub(crate) async fn ndn_from_ext(
     context: &Context,
     failed: &FailedMsg,
diff --git a/src/mimeparser.rs b/src/mimeparser.rs
index b9fe3792d..8d864c226 100644
--- a/src/mimeparser.rs
+++ b/src/mimeparser.rs
@@ -933,7 +933,9 @@ impl MimeMessage {
         None
     }
 
-    /// Handle reports (only MDNs for now)
+    /// Handle reports
+    /// (MDNs = Message Disposition Notification, the message was read
+    /// and NDNs = Non delivery notification, the message could not be delivered)
     pub async fn handle_reports(
         &self,
         context: &Context,
diff --git a/src/sql.rs b/src/sql.rs
index 5c54e6f68..a0c26e6e9 100644
--- a/src/sql.rs
+++ b/src/sql.rs
@@ -1242,7 +1242,7 @@ async fn open(
             sql.set_raw_config_int(context, "dbversion", 63).await?;
         }
         if dbversion < 64 {
-            info!(context, "[migration] v63");
+            info!(context, "[migration] v64");
             sql.execute(
                 "ALTER TABLE msgs ADD COLUMN error TEXT DEFAULT '';",
                 paramsv![],