Use DEFAULT_FROM_EMAIL instead of EMAIL_HOST_USER for the from email address if EMAIL_HOST_USER does not have an "@" sign in it.

Some email relay services require a username that is not an email address for the EMAIL_HOST_USER (e.g.: https://sendgrid.com/docs/API_Reference/SMTP_API/integrating_with_the_smtp_api.html)

mfa/Common.py

@@ -2,7 +2,10 @@ from django.conf import settings
 from django.core.mail import EmailMessage
 
 def send(to,subject,body):
-    From = "%s <%s>" % (settings.EMAIL_FROM, settings.EMAIL_HOST_USER)
+    from_email_address = settings.EMAIL_HOST_USER
+    if '@' not in from_email_address:
+        from_email_address = settings.DEFAULT_FROM_EMAIL
+    From = "%s <%s>" % (settings.EMAIL_FROM, from_email_address)
     email = EmailMessage(subject,body,From,to)
     email.content_subtype = "html"
     return email.send(False)