diff --git a/test/test_send_mail.py b/test/test_send_mail.py
index 01bb6a755bbf47f25cd111d45685016637eb0373..b35abfe7ddfaf78b1581f95e5ba613e2e1a21f61 100644
--- a/test/test_send_mail.py
+++ b/test/test_send_mail.py
@@ -6,6 +6,15 @@ from compendium_v2.db.auth_model import User
 from compendium_v2.email import send_admin_signup_notification, send_user_signup_notification
 
 
+class MockedThread(object):
+    def __init__(self, target, args):
+        self.target = target
+        self.args = args
+
+    def start(self):
+        self.target(*self.args)
+
+
 def decode_message(msg: MIMEMultipart):
     message: List[MIMEText] = msg.get_payload()
     text: MIMEText = message[0]
@@ -30,10 +39,15 @@ def test_signup_email_admin(app, mocked_admin_user, mocker):
     def _send_mail(*args, **kwargs):
         _msg = args[-1]
         decoded = decode_message(_msg)
+        _from = _msg['From']
+        _to = _msg['To']
+        assert _from == 'fakesender123@test.local'
+        assert _to == 'testemail123@email.local'
         message = 'testname has just signed up with the email testmail321@email.com and provider ID testsub'
         assert decoded == message
 
     mocker.patch('compendium_v2.email._send_mail', _send_mail)
+    mocker.patch('threading.Thread', MockedThread)
     with test_user(app) as user:
         send_admin_signup_notification(user)
 
@@ -42,9 +56,14 @@ def test_signup_email_user(app, mocker):
 
     def _send_mail(*args, **kwargs):
         _msg = args[-1]
+        _from = _msg['From']
+        _to = _msg['To']
+        assert _from == 'fakesender123@test.local'
+        assert _to == 'testmail321@email.com'
         decoded = decode_message(_msg)
         assert len(decoded) > 50  # check that there's a message
 
     mocker.patch('compendium_v2.email._send_mail', _send_mail)
+    mocker.patch('threading.Thread', MockedThread)
     with test_user(app) as user:
         send_user_signup_notification(user, 'testname')