Yosemite: Power Nap enabled on a 2011 iMac?

Hello everyone. I have a 27 inch iMac mid 2011 with both SSD and 2 GB Hard Drive. I never turn off in the night, I prefer to standby it with Stop. After I installed OS X Yosemite my iMac is turning on sometime in the night (about 2-3 times in a night). Staying on 1 up to 3 minutes, then going to Stop again. In the past, this was happening when the option "Activate for Network Access" was selected in Power Saving Pref Pane. Now is unselected, and I can't see any Power Nap option, of course, my Mac is too old for that, but it's behaving like Power Nap is acting. For example, new Mail messages are downloaded already in the morning. This is very boring, because the computer is in a bedroom. What to do? Any ideas? Thank you for reading!

My Power Management pref file is shown here:

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">

<plist version="1.0">

<dict>

<key>ActivePowerProfiles</key>

<dict>

<key>AC Power</key>

<integer>-1</integer>

</dict>

<key>Custom Profile</key>

<dict>

<key>AC Power</key>

<dict>

<key>Automatic Restart On Power Loss</key>

<false/>

<key>Disk Sleep Timer</key>

<integer>0</integer>

<key>Display Sleep Timer</key>

<integer>5</integer>

<key>Display Sleep Uses Dim</key>

<integer>1</integer>

<key>Hibernate File</key>

<string>/var/vm/sleepimage</string>

<key>Hibernate Mode</key>

<integer>0</integer>

<key>PrioritizeNetworkReachabilityOverSleep</key>

<integer>0</integer>

<key>Sleep On Power Button</key>

<integer>1</integer>

<key>System Sleep Timer</key>

<integer>10</integer>

<key>TTYSPreventSleep</key>

<integer>1</integer>

<key>Wake On LAN</key>

<integer>0</integer>

</dict>

</dict>

</dict>

</plist>