I have a very strange problem with my upgrade to V15 from v12.5 I had v12.5 on a win7 x64 machine and had some problems with the initial upgrade and during talks with tech support decided to install v15 on a server 2008 r2 license that I had. I created a new vmware instance, installed server 2008 r2 and everything looks good. Ran the 3cx install with a backup of my v12.5 system and everything looks perfect... until I get to the mail setup. I try sending a test email and after several seconds it responds "Operation cancelled." I tried numerous things and eventually tried changing the IP address of the new machine to something different and it works perfectly so - I know it's not a firewall issue (when I bring up the old machine on 192.168.xx.7 it works fine sending email. I take it offline and power up the new machine on 192.168.xx.7 and mail sending fails. Go to network settings and change to 192.168.xx.6 and mail works perfectly. What could be interfering with mail sending on a specific IP address?