I could swear I saw an option to prohibit users from signing up with free email addys (yahoo, hotmail, gmail, aol, etc...), but I cannot find it. Am I dreaming or is that feature in aMember? My testing shows that delivery to these services is VERY unreliable and unpredictable via php.
If your emails aren't getting delivered, go through the following check-list 1. Setup an "abuse@mydomain.com" account 2. Setup a "postmaster@mydomain.com" account 3. Verify your reverse DNS. Use DNSreport.com to verify. 4. Added an SPF record for your domain? Denied Email address list Does your hosting company limit the number of emails per hour you may send? Check this, and if so, buy the phpList plugin and configure the throttling settings in config.php. 6. Do you include a note in your email asking people to "safe list" (or add to their address book) your sending-from email address, "my-sending-address@mydomain.com"? 7. Have you checked your bounced mail account setup? If you've done the above, then you could try blocking email addresses of a specific domain aMember CP -> Setup/Configuration -> Ban -> Denied Email address list Fill in list like: *@yahoo.com *@hotmail.com *@aol.com etc. Note that most people use free email services. I strongly recommend you don't use this setting. Hope this is helpful.