How's been your email with Telus? Since I've updated my 27" 2011 imac everything's been great except Mail went down. Do a search and you'll find more than a few people have had issues. I've managed the work-a-round some have said to do but who knows how long it'll last. Here's one link... https://timthetechguy.wordpress.com/2014/10/17/yosemite-telus-email-issues-workaround/ Btw, before I install I made a usb bootdisk.