melib/imap: don't retry watch conn on non-network error

melib/src/backends/imap.rs

@@ -499,6 +499,8 @@ impl MailBackend for ImapType {
                 let mut main_conn_lck = timeout(uid_store.timeout, main_conn.lock()).await?;
                 if err.kind.is_network() {
                     uid_store.is_online.lock().unwrap().1 = Err(err.clone());
+                } else {
+                    return Err(err);
                 }
                 debug!("Watch failure: {}", err.to_string());
                 match timeout(uid_store.timeout, main_conn_lck.connect())

melib/src/backends/imap/watch.rs

@@ -408,14 +408,16 @@ pub async fn examine_updates(
             }
         }
         if uid_store.keep_offline_cache {
-            cache_handle
-                .insert_envelopes(mailbox_hash, &v)
-                .chain_err_summary(|| {
-                    format!(
-                        "Could not save envelopes in cache for mailbox {}",
-                        mailbox.imap_path()
-                    )
-                })?;
+            if !cache_handle.mailbox_state(mailbox_hash)?.is_none() {
+                cache_handle
+                    .insert_envelopes(mailbox_hash, &v)
+                    .chain_err_summary(|| {
+                        format!(
+                            "Could not save envelopes in cache for mailbox {}",
+                            mailbox.imap_path()
+                        )
+                    })?;
+            }
         }
 
         for FetchResponse { uid, envelope, .. } in v {