I have installed UrBackup 1.4.14 on CentOS 6.6 and i don’t get the option to configure mail server.
UrBackup 1.4.14 is the latest version available for CentOS, whereas i have tested on Windows version of UrBackup and noticed Mail server settings available and working fine.
By the looks on how the testing has gone in the forums recently, I think that CentOS UrBackup Server is a little depreciated.
CentOS Server: 1.4.14
Windows Server: 2.0.33
However, Linux clients (and this may be a debian thing) have a 2.0.32 Client.
Check if you have curl installed on server.