you're right, it does only block inbound traffic, but since you need to handshake (request and acknowledge) a file transfer, it might be going out but never recieving an acknowledgement back that it's ok to transfer to so-and-so@wherever.com at that address. If you were blindly sending it UDP like an email that'd be a different story. I'm pretty sure the firewall is enabled if this is happening. Couldn't you just add a rule though in ICF for IM? Not sure what ports they are though off the top of my head, I don't really use IM much...