I think this error occurred because either your IP address did not allow reverse lookup, or it belonged to a non-JP block. (I introduced this hack after quite a few spam posts from overseas.)
Could you please email me your IP address(es) so I can add them to the white list?
(I hope everyone use this Forum instead of the anonymous TeX Q&A.)
Ahh, I understand. No need. It was send from a WLAN account within the JAIST, so not resolvable from outside. I used a wired computer now and that worked.
I use the Forum in general, but sometimes answer to posts in the QA.