diff --git a/scripts/mx_tag_carriers.py b/scripts/mx_tag_carriers.py
index 6d3a6a6..cec97f1 100644
--- a/scripts/mx_tag_carriers.py
+++ b/scripts/mx_tag_carriers.py
@@ -98,28 +98,27 @@ def main() -> int:
     domains = [r[0] for r in cur.fetchall() if r[0]]
     print(f"resolving MX for {len(domains)} distinct domains (concurrent)...", file=sys.stderr)
 
-    # Resolve concurrently -- DNS is I/O-bound, so a thread pool gives a huge
-    # speedup over the serial 3s-timeout-per-domain path.
-    results: dict[str, str] = {}
-    done = 0
-    with ThreadPoolExecutor(max_workers=40) as ex:
-        for dom, prov in zip(domains, ex.map(classify, domains)):
-            results[dom] = prov
-            done += 1
-            if done % 500 == 0:
-                print(f"  resolved {done}/{len(domains)}", file=sys.stderr)
-
-    # Batch-write the tags.
+    # Resolve concurrently and write incrementally as each completes, so a few
+    # slow/hung domains never hold up the whole batch (as_completed, not map).
+    from concurrent.futures import as_completed
     tagged = 0
-    for dom, prov in results.items():
-        cur.execute("""
-            UPDATE fmcsa_carriers SET mx_provider = %s
-            WHERE lower(split_part(email_address, '@', 2)) = %s
-              AND mx_provider IS NULL
-        """, (prov, dom))
-        tagged += 1
-        if tagged % 500 == 0:
-            conn.commit()
+    with ThreadPoolExecutor(max_workers=60) as ex:
+        futs = {ex.submit(classify, d): d for d in domains}
+        for fut in as_completed(futs):
+            dom = futs[fut]
+            try:
+                prov = fut.result()
+            except Exception:
+                prov = "no_mx"
+            cur.execute("""
+                UPDATE fmcsa_carriers SET mx_provider = %s
+                WHERE lower(split_part(email_address, '@', 2)) = %s
+                  AND mx_provider IS NULL
+            """, (prov, dom))
+            tagged += 1
+            if tagged % 300 == 0:
+                conn.commit()
+                print(f"  tagged {tagged}/{len(domains)} domains", file=sys.stderr)
     conn.commit()
 
     # Report the operator distribution of what we just tagged.