If you don’t receive your confirmation mail after registration, or notifications of subscribed threads, the reason could be that your ISP and/or mailprovider is using the services of BarracudaCentral.
Unfortunately, every now and then this shady service lists the server-IP on which this forum runs as “doubtful” or whatever else. And for no apparent reason. This Barracuda score is then used by spam-protection tools and can result in non-delivery of mails.
I am taking good care of the server and keep it safe and uptodate, and of 104 Anti-Spam-Lists it is only Barracuda having issues. Even when I apply there to be removed, this takes ages (or is not done at all), and only to become listed after some time again.
Sorry to say, but these guys are bandits in my view. They offer an option to get whitelisted – against payment of course. Fork them!
So if you don’t get the mails, this could be the cause. Inquire whether Barracuda is involved anywhere in your mail chain, and ditch the bitch!
There is nothing I can do about it, unfortunately.