Is the SMTP connection failing ?
This line ? if(client.connect(server,25)
Or is the complete ethernet connection failing ?
This line ? Ethernet.begin(...
Could you try the webserver with DHCP sketch.
To see if you can create a webpage and connect to it with a browser.
That example is old, please use DHCP by omitting the 'ip' parameter and use Ethernet.begin( mac);
Tell us what the output of the serial monitor is.