The core issue is that ttf-mscorefonts-installer files are repeatedly failing to download, so you are repeatedly emailed about it. (The email sure could be improved.)
update-notifier handles the downloads, but the actual downloads are performed by apt-helper, and that program has trouble following redirects with spaces in the URL and handling files that already exist on the target machine.
The core issue is that ttf-mscorefonts -installer files are repeatedly failing to download, so you are repeatedly emailed about it. (The email sure could be improved.)
update-notifier handles the downloads, but the actual downloads are performed by apt-helper, and that program has trouble following redirects with spaces in the URL and handling files that already exist on the target machine.
Have a look at the following bug report about that: https:/ /bugs.launchpad .net/ubuntu/ +source/ update- notifier/ +bug/1655431