As you may know, the forum software attempts to reject membership requests from known spammer IP addresses, but as it's an "arms race" as they say, some spammers do slip through.
Then I need to try an ascertain if the membership request is legitimate or a spammer. I can check the email address and IP address using some search tools, but sometimes it is difficult to determine whether a specific membership request is a real person interested in our forum or simply a spammer.
If you have attempted to join our forum and not had a reply back, it may be because I could not determine from your hotmail or gmail account if you are a real person or not. If you haven't had a membership request approved and you would like to join, I would first suggest that you try to register using your university or corporate email address. No other members (except the forum administrators) will see your actual email address, and we should be able to approve you right away.
If that doesn't work, please contact me directly by email and provide your name, professional affiliation and your reason for joining the forum. That should be enough information for us to determine that you are a real person.