diff --git a/src/server/BreCal/services/schedule_routines.py b/src/server/BreCal/services/schedule_routines.py
index e778d58..61e36cc 100644
--- a/src/server/BreCal/services/schedule_routines.py
+++ b/src/server/BreCal/services/schedule_routines.py
@@ -153,13 +153,14 @@ def SendEmails(email_dict):
             logging.warning("Unknown email encryption '%s'; defaulting to STARTTLS.", encryption)
             conn.starttls()
             conn.ehlo()
+        auth_username = defs.email_credentials.get("auth_username") or defs.email_credentials.get("sender")
         if use_ntlm_auth:
-            ntlm_user = defs.email_credentials.get("ntlm_user") or defs.email_credentials["sender"]
+            ntlm_user = defs.email_credentials.get("ntlm_user") or auth_username
             ntlm_domain = defs.email_credentials.get("ntlm_domain")
             ntlm_workstation = defs.email_credentials.get("ntlm_workstation")
             _smtp_auth_ntlm(conn, ntlm_user, defs.email_credentials["password_send"], domain=ntlm_domain, workstation=ntlm_workstation)
         else:
-            conn.login(defs.email_credentials["sender"], defs.email_credentials["password_send"])
+            conn.login(auth_username, defs.email_credentials["password_send"])
 
         current_path = os.path.dirname(os.path.abspath(__file__))