Probably it'sin your antispam list (keyword = travel, perhaps). It's not in mine. Check your antispam list in the back office.

Found it. Go to your antispam settings in the back office. In the filter dialog box type ya and click 'filter list'. It will show 'ya.com'. Now uncheck it (the green finch before the url). Now your url will be allowed.

Uff, That was it.

Thanks a lot (I couldn't find it)

Okay thanks. That keyword is way too short. It obviously can catch all sorts of domains instead of just the malicious spammer "ya.com". I just published ".ya.com" and removed "ya.com" from the official master keyword list. Future users won't find that in their updates, but current users (who already have an updated antispam list) will have to remove it from their local table.