I checked the log folder of Allocatus and it reports:

Cannot send e-mail notification to smtp server. Allocatus will retry on next sync. Please check smtp server address in Allocatus Server Configuration and make sure relaying is allowed.

Please contact your mail server admin and ask him to allow anonymous relay for the IP-address of your Allocatus/Project Server. Here are some starting points: 

Exchange Server 2010
http://technet.microsoft.com/en-us/library/bb232021.aspx

Domino Server 8.5
http://publib.boulder.ibm.com/infocenter/domhelp/v8r0/index.jsp