diff --git a/crates/admin/src/migrate.rs b/crates/admin/src/migrate.rs
index 4de0896..0005e5f 100644
--- a/crates/admin/src/migrate.rs
+++ b/crates/admin/src/migrate.rs
@@ -2,7 +2,7 @@ use std::path::{Path, PathBuf};
 
 use bichon_core::migrate::{
     count_eml_segments, do_migrate_segment, is_tantivy_index_dir,
-    store::{LegacyDirs, NewDirs},
+    store::{LegacyDirs, NewDirs, NewIndexWriter},
 };
 use console::style;
 use dialoguer::{theme::ColorfulTheme, Confirm, Input};
@@ -326,6 +326,18 @@ pub fn handle_migration(theme: &ColorfulTheme) {
             .progress_chars("#>-"),
     );
 
+    let mut writer = match NewIndexWriter::open(NewDirs::new(
+        new_index_path.clone(),
+        new_data_path.clone(),
+    )) {
+        Ok(w) => w,
+        Err(e) => {
+            pb.finish_with_message(format!("{}", style("Migration failed.").red()));
+            eprintln!("\n{} {:?}", style("✘").red().bold(), e);
+            return;
+        }
+    };
+
     let mut grand_total_migrated: usize = 0;
     let mut grand_total_skipped: usize = 0;
 
@@ -337,7 +349,7 @@ pub fn handle_migration(theme: &ColorfulTheme) {
         match do_migrate_segment(
             batch_size,
             legacy,
-            NewDirs::new(new_index_path.clone(), new_data_path.clone()),
+            &mut writer,
             seg_idx,
             |msg| {
                 if let Some(data) = msg.strip_prefix("TOTAL:") {
@@ -407,6 +419,13 @@ pub fn handle_migration(theme: &ColorfulTheme) {
         pb.set_position((seg_idx + 1) as u64);
     }
 
+    pb.set_message(style("Finalizing indexes...").dim().to_string());
+    if let Err(e) = writer.finish_writers() {
+        pb.finish_with_message(format!("{}", style("Migration failed.").red()));
+        eprintln!("\n{} {:?}", style("✘").red().bold(), e);
+        return;
+    }
+
     pb.finish_with_message(format!(
         "Migration finished. Total: {}, Skipped: {}",
         grand_total_migrated, grand_total_skipped
diff --git a/crates/core/src/cache/imap/download/flow.rs b/crates/core/src/cache/imap/download/flow.rs
index cdb3842..36805a7 100644
--- a/crates/core/src/cache/imap/download/flow.rs
+++ b/crates/core/src/cache/imap/download/flow.rs
@@ -339,6 +339,17 @@ pub async fn fetch_and_save_full_mailbox(
     Ok(max_uid)
 }
 
+/// Generates a synthetic UIDVALIDITY for IMAP servers that don't provide it.
+/// Uses a stable hash of the mailbox name to ensure consistent IDs across sessions.
+fn generate_synthetic_uidvalidity(mailbox_name: &str) -> u32 {
+    use std::collections::hash_map::DefaultHasher;
+    use std::hash::{Hash, Hasher};
+    
+    let mut hasher = DefaultHasher::new();
+    mailbox_name.hash(&mut hasher);
+    (hasher.finish() as u32).wrapping_add(1) // Avoid 0, which might be reserved
+}
+
 pub async fn reconcile_mailboxes(
     account: &AccountModel,
     remote_mailboxes: &[MailBox],
@@ -366,30 +377,30 @@ pub async fn reconcile_mailboxes(
                 break;
             }
 
-            let new_highest_uid = if local_mailbox.uid_validity != remote_mailbox.uid_validity {
-                if remote_mailbox.uid_validity.is_none() {
-                    let err_msg = format!(
-                        "Mailbox '{}' logic error: Server did not provide UIDVALIDITY.",
-                        local_mailbox.name
+            // Handle missing UIDVALIDITY from non-compliant IMAP servers
+            // (e.g., Tencent Enterprise Mail, etc.)
+            let remote_uid_validity = match remote_mailbox.uid_validity {
+                Some(uid) => uid,
+                None => {
+                    // Generate a synthetic UIDVALIDITY based on mailbox name
+                    let synthetic_uid = generate_synthetic_uidvalidity(&remote_mailbox.name);
+                    
+                    warn!(
+                        "Account {}: Mailbox '{}' - Server did not provide UIDVALIDITY. \
+                        Using synthetic UIDVALIDITY {} based on mailbox name. \
+                        This mailbox will be synced but may require periodic rebuilds if the server's mailbox structure changes.",
+                        account_id, remote_mailbox.name, synthetic_uid
                     );
-
-                    warn!("Account {}: {}", account_id, err_msg);
-
-                    DownloadState::update_folder_progress(
-                        account_id,
-                        remote_mailbox.name.clone(),
-                        0,
-                        0,
-                        FolderStatus::Failed,
-                        Some(err_msg.clone()),
-                    )?;
-                    DownloadState::append_session_error(account_id, err_msg)?;
-                    continue;
+                    
+                    synthetic_uid
                 }
+            };
+
+            let new_highest_uid = if local_mailbox.uid_validity != Some(remote_uid_validity) {
                 info!(
                     "Account {}: Mailbox '{}' detected with changed uid_validity (local: {:#?}, remote: {:#?}). \
                     The mailbox data may be invalid, resetting its envelopes and rebuilding the cache.",
-                    account_id, local_mailbox.name, &local_mailbox.uid_validity, &remote_mailbox.uid_validity
+                    account_id, local_mailbox.name, &local_mailbox.uid_validity, &remote_uid_validity
                 );
 
                 DownloadState::update_folder_progress(
@@ -443,6 +454,10 @@ pub async fn reconcile_mailboxes(
 
             let mut updated = remote_mailbox.clone();
             updated.highest_uid = new_highest_uid;
+            // Update uid_validity with the resolved value (either from server or synthetic)
+            if updated.uid_validity.is_none() {
+                updated.uid_validity = Some(remote_uid_validity);
+            }
             mailboxes_to_update.push(updated);
         }
         //The metadata of this mailbox must only be updated after a successful synchronization;
diff --git a/crates/core/src/migrate/mod.rs b/crates/core/src/migrate/mod.rs
index 02f15aa..80255cd 100644
--- a/crates/core/src/migrate/mod.rs
+++ b/crates/core/src/migrate/mod.rs
@@ -121,7 +121,7 @@ fn is_dir_not_empty(path: &PathBuf) -> std::io::Result<bool> {
 pub fn do_migrate_segment<F>(
     batch_size: u32,
     legacy: LegacyDirs,
-    new_dirs: NewDirs,
+    writer: &mut NewIndexWriter,
     segment_index: usize,
     mut on_progress: F,
 ) -> BichonResult<()>
@@ -226,8 +226,6 @@ where
     drop(envelope_index);
 
     // ── Phase 2: process EML docs, streaming one at a time ─────────────
-    let mut writer = NewIndexWriter::open(new_dirs)?;
-
     let mut total_migrated = 0usize;
     let mut total_skipped = 0usize;
 
@@ -308,7 +306,6 @@ where
         chunk_start = chunk_end;
     }
 
-    writer.finish_writers()?;
     on_progress(&format!("DONE:{}:{}", total_migrated, total_skipped));
     Ok(())
 }