As per this django-invitations issue, django-invitations considers an invite "accepted" if the invite link is clicked. This is problematic for two reasons (or more):
- Automatic mail crawlers which visit links checking for malware etc., and verifying that you're not a spammer
- A user which clicks a link to "check out" an invite, but doesn't necessarily want to sign up right now
Something to consider is that this solution assumes you're using django-allauth as it uses the EmailAddress model of that package.