Refresh timer ignored

[Birger52]

In settings you can set how often to check for new mail.
It is set to every 60. minute.
So software actually looks for email every 5 minutes.
(See img. attached)
It  may be, it is simply to "keep alive" the connection.
So ... Why is it nescessary to "Keep alive" when there it is not looking for new mail?
Where do I change the setting, for Keep alive interval?