I have gotten reports from my members that they didn't receive their activation emails and I am not receiving any mail from the contact page. I have checked the User Email Logs and it shows that three messages were sent. I have checked and changed the admin email a couple of times and checked my spam folder on both accounts.
the first thing to check is this
doc about mail issues...
and some web hosts have restriction that either the "From" or the "To" address must be of same domain as the website for the PHP mails to work.. make sure that isnt the case with your hosts...
Sometimes your members have issues with certain providers. It's best to make users sign up with a GMail so that it works for them.