Actually no, the Forums are not dead. We read the posts, but we not always have the chance to reply due to different replies.
Since it looks like FO is quite critical for your business as you said "no response from the developer clearly, costs money.", I strongly suggest you getting at least a Basic Support Plan and that way you would get a response in a timely manner. Otherwise, I am afraid we can reply only when we have enough time...
As for the problem, we know of many people using cyrillic characters (and many others) in their emails without experiencing any problems, so it could be a server side issue... or why not, it could also be the mail server too.
In order to look into this problem further, we would need to access the email you mention, and know your server settings, but for this to happens, due to different policies but mainly because of security and confidentiality ones which you may understand, we can do so only if you get a Support Plan first. If you are interested in this, feel free to drop me a private message.
BR,
Francisco
