MacOS – Hosts file being reset after every reboot

What causes mail to go offline is authentication errors. You must contact whomever is in charge of your mail authentication servers and ask them to resolve the issue. At my work mail going offline is almost considered normal due to the fact that our internet access must pass through our network proxies which often cause mail connections to fail authentication.

Fixed:

This thread on the Apple forums is the key:

• Open the Library folder in your Home folder.
• In the Library folder, open the Application Support folder.
• Locate the folder named NotificationCenter. Drag this folder to the desktop.
• Next, open the Terminal application and enter the following

.

cd `getconf DARWIN_USER_DIR`
rm -rf com.apple.notificationcenter 
killall usernoted; killall NotificationCenter

• Restart your computer.

The issue is clearly to do with the NotificationCenter database. There are 3 files:

• db
• db-shm
• db.wal

In my case db.wal was a 0 byte file compared with 1.9MB on a correctly working Yosemite install. Permissions were correctly set, but looks as if Yosemite wasn't writing to it. Only deleting db.wal didn't fix the problem - another 0 byte file was created on restart. Deleting everything works though!