Received an email that my Apple photo stream will be shut down. What does this mean? Is this legit?

It sounds like you might possibly still be using My Photo Stream vice the newer iCloud Photos system.

Of course, scammers almost ALWAYS capitalize on the confusion surrounding these sorts of announcements to “ply their trade” so BEWARE.

You might not even be using My Photo Stream (i.e. you’re already on iCloud Photos)

See this for more info:

Information about the My Photo Stream shutdown – Apple Support (AU)

I do not have an album specifically named photo stream. Does that mean I am already on Cloud photos?

I’ve had the same email which appears to be legitimate (judging by sender’s email). No idea what to do

I have I could photos enabled - do I need to do anything else?

Same here; my wife is getting these but I put her on iCloud/iPhoto long ago.

I GET "Digitally Certified Email" when clicking on the email 'From'

Email looks legit from noreply@email.apple.com