These days it's getting harder and harder for any company to use e-mail reliably. If you have a public web site with e-mail addresses on it, you get swamped with spam.
I run my own software business; my "support" e-mail address receives typically 4000-5000 emails per day, 99.5% spam. If I didn't use spam-blocking technology, I couldn't begin to cope with the e-mail. I do use such technology because I have to, as does every company. The inevitable consequence of that is that if you are unfortunate enough to be sending mail from the same server as a currently-active spammer (blacklist operate, at least partially, using the IP address of the mail server), your e-mail won't get through.
It works the other way too. I'd estimate that about one in four or five of the e-mails I send to my customers doesn't reach them because of spam-blocking. That inevitably leads to irate customers who say "why aren't you answering my e-mail", which is very fraustrating when I am answering them and my reply isn't reaching them. There is, for example, a large American ISP called "earthlink". When I see an "earthlink.net" address my heart sinks because I know for a fact it'll bounce any reply I send to it (they seem to block virtually all international e-mail).
I wouldn't be so quick to blame Bookeen. Perhaps your mail isn't reaching them. Perhaps their e-mail isn't reaching you. That's why I'm suggesting that you try sending your mail from a different source and seeing if you have any better luck that way.
It's a no-win situation.