I've done a little investigating about this and have found some pertinent information.
Yahoo is temporarily deferring email from the forum server "...due to user complaints." How about that. It's hard to get email from the forum server if you lodge complaints with your email service about getting the emails! 
This will cause mail delivery to people with Yahoo email addresses to be delayed. AOL uses Yahoo mail servers on the back end, so that's why those of you with AOL addresses are having problems, too. It also sounds like a lot of you are finding your email notifications in your spam folder. All the complaints about missing or delayed emails in this thread (with one exception) are from people with either Yahoo or AOL email addresses.
One way to help this is to be sure you have whitelisted email coming from crowdstack.com. Also, add the email address "alerts@crowdstack.com" to your address book. JohnH, "whitelisting" is a procedure where you specifically tell your email provider that emails from the domain crowdstack.com are not spam and you want to receive them.
Unfortunately, we can't do anything about Yahoo/AOL deferring the email, we just have to hope they decide to start delivering it when they receive it.
