Isa and smtp virtual are listening on the same port (25). I've changed it to another port but the problem is that we cannot receive mails from our isp. Our ISP is hosting our domain and forwarding all our emails to our fixed IP connected with a lease line. ISP ---|Lease line| ---> |ISA with Vsmtp| ------> |Exchange 5.5| I don't know should I put on the virtual smtp to be able to accept emails from the ISP. Thanks for your reply