Край Lync и Exchange Server: как иметь доступ к моему обменному почтовому ящику от внешней сети и также к OWA

What you probably need is a Firewall / Reverse Proxy in front of all your servers e.g. Something link Microsoft Forefront TMG.

That is then set up with your external IP address and routes all inbound web requests to the various boxes (Lync, OWA etc.) based on a set of "Publishing Rules"

Note that the above is a very simplistic description of what is a potentially a more complicated project and doesn't reflect the amount of effort and knowledge you will need in order to set this up.

I suggest you read up on firewalls and reverse proxies in order to gain more insight into your options.