diff --git a/atomizer.py b/atomizer.py
index 0991395..ecdcadf 100755
--- a/atomizer.py
+++ b/atomizer.py
@@ -54,6 +54,8 @@ def __init__(self, loop, target, threads=3, debug=False):
         self.sprayer = None
         self.threads = int(threads)
         self.debug = debug
+        # Maximum 3 concurrent tasks per thread.
+        self.sync = asyncio.BoundedSemaphore(self.threads * 3)
 
         log_format = '%(threadName)10s %(name)18s: %(message)s' if debug else '%(message)s'
 
@@ -83,6 +85,10 @@ def imap(self, port):
             port=port
         )
 
+    def _atomize(func, username, password, sync):
+        func(username, password)
+        sync.release()
+
     async def atomize(self, userfile, password):
         log = logging.getLogger('atomize')
         log.debug('atomizing...')
@@ -91,13 +97,15 @@ async def atomize(self, userfile, password):
 
         log.debug('creating executor tasks')
         logging.info(print_info(f"Starting spray at {get_utc_time()} UTC"))
-        blocking_tasks = [
-            self.loop.run_in_executor(self.executor, partial(auth_function, username=username.strip(), password=password))
-            for username in userfile
-        ]
+
+        pending = []
+        for username in userfile:
+            await self.sync.acquire()
+            task = self.loop.run_in_executor(self.executor, partial(Atomizer._atomize, auth_function, username.strip(), password, self.sync))
+            pending.append(task)
 
         log.debug('waiting for executor tasks')
-        await asyncio.wait(blocking_tasks)
+        await asyncio.wait(pending)
         log.debug('exiting')
 
     async def atomize_csv(self, csvreader: csv.DictReader, user_row_name='Email Address', pass_row_name='Password'):