Ok. I got this working now.

Firstly: I can't remember for sure, but I think I got verification mail to my email when I first created my account and followed the link so that my account was activated.

Still I couldn't reply any messages. I changed my email from own domain to gmail account and got new activation mail, after that account did indeed get properly activated and now I can reply.

The weird thing is that I never got reactivation email to my first email account. Well thanks for pointing out that some emails simply does not work.