Oct 03, 2015 This videos leaves the usual theme of the channel, but I thought it would be helpful. After upgrading to OSX El Capitan, I found all my Mail messages were gone. Restoring my computer to my back-up. Oct 21, 2015  Download. The OS X El Capitan 10.11.1 update improves the stability, compatibility, and security of your Mac, and is recommended for all users. This update: Improves installer reliability when upgrading to OS X El Capitan. Improves compatibility with Microsoft Office 2016. Fixes an issue where outgoing server information may be missing from Mail.

If you have a mid 2009 MacBook Pro, you can't update the OS. To update, you need a MacBook Pro (Mid 2010 or later) Model 6.2 and higher.

If you are careful about what you download and where you search on the Internet, your computer is useable without the latest security updates. My last computer had a 10.6 partition which I used every night. That was after El Capitan was released, so the OS was 5 versions behind. By being careful, I never had any problems.

Update From El Capitan

I would make sure that you had at least 2 separate backups on 2 separate drives in case you have problems. That will allow you to recover.