Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
Sparrow Adds Support for POP Email Accounts To iPhone App –
Not to long ago we the well known mail client Sparrow arrive on the iPhone but was soon criticised as the app did not include POP or push notifications.
Today support for POP email accounts arrived today and Sparrows developers have promised that push notifications are coming in a future update
The New Web :
The developers behind the popular Apple-focused email client Sparrow have today pushed a new update for its iPhone application, bringing its mobile client on par with the desktop version with the inclusion of full POP support.