Yahoo and AOL have recently changed their e-mail policy. Their policy says that e-mails which are sent from a yahoo or AOL address must go through the Yahoo or AOL server, otherwise the mail may be rejected.
So what does this mean, in English? It means that since you're using the Golf League Tracker mail server to send e-mails, that your mail might not get through if you're sending using Yahoo.com or Aol.com "from" email address.
So what can you do? Unfortunately, there's nothing Golf League Tracker can do, since this is a policy implemented by those respective companies. What I would suggest is that you open a non-yahoo or non-aol e-mail account.
If you'd get into the more technical details of this policy change, take a look at this blog post.