As far as I know they need 5 ml EDTA for the research.
I also did send some EDTA tubes in a normal envelop
(with bubble plastic inside, like sending for Dvd's) by normal mail.
Is it also a problem in Bulgaria when you send to a lab in this way?
Otherwise you maybe can send by normal post to a wolfdog owner in another country!
(and he/she can send it to Bern for you)