When someone sends you resources (and possibly vice versa) a incoming trade notification will pop up. Though instead of swords, like the incoming attack notification there are pictures of resources. Replying to Kinglurker, yes you would be able to turn it off in setting if you don't find it useful.
Proposal:
When someone sends you resources you get a notification.
Have you Checked the DNS and PSI lists in the Archives? Is this idea similar to one that has been previously suggested?
Briefly and I believe not.
Reason:
If you have lots of cities then you don't want to spend all your...