Revert "use async in email handler"

This reverts commit 4d7cd09847.

email_handler.py

@@ -31,7 +31,6 @@ It should contain the following info:
 
 """
 import argparse
-import asyncio
 import email
 import os
 import time
@@ -1712,7 +1711,7 @@ def should_ignore(mail_from: str, rcpt_tos: List[str]) -> bool:
     return False
 
 
-async def handle(envelope: Envelope) -> str:
+def handle(envelope: Envelope) -> str:
     """Return SMTP status"""
 
     # sanitize mail_from, rcpt_tos
@@ -1935,7 +1934,7 @@ async def handle(envelope: Envelope) -> str:
 class MailHandler:
     async def handle_DATA(self, server, session, envelope: Envelope):
         try:
-            ret = await self._handle(envelope)
+            ret = self._handle(envelope)
             return ret
         except Exception:
             LOG.e(
@@ -1946,7 +1945,7 @@ class MailHandler:
             return status.E404
 
     @newrelic.agent.background_task(application=newrelic_app)
-    async def _handle(self, envelope: Envelope):
+    def _handle(self, envelope: Envelope):
         start = time.time()
 
         # generate a different message_id to keep track of an email lifecycle
@@ -1959,7 +1958,9 @@ class MailHandler:
             envelope.rcpt_tos,
         )
 
-        ret = await handle(envelope)
+        app = new_app()
+        with app.app_context():
+            ret = handle(envelope)
             elapsed = time.time() - start
             LOG.i(
                 "Finish mail from %s, rctp tos %s, takes %s seconds <<===",