In browser version at least (mozilla firefox), the blinking for mail button is very persistent in the same logged session.

Steps to reproduce:
1. click to check mail
2. go to fortress or underworld and claim money/resource
3. mail button blinks again

EDIT this seems to happen after arena fight too.

Would you please consider to limiting blinking once per logged session?

Its really good to be reminded about the upcoming event! Just not all the time...