Open Ports

I have a W2K server with EX5.5 on it running behing MS Proxy 2.0. I recently ran netstsat -a from the command line on the Exchange server to find that I have a number of entries on different ports listed with "freemail.com.au" in the foreign address column. I have no idea how it got there, but I can't get rid of it. It's from Australia and I'm in the US, so it's nothing my users are doing. Does anyone have any idea on what this is doing in there? There are numerous local ports ranging from 25 all the way up to 42510. I'm sure it changes once in a while.