Exploit/ransomware

It's a scam. In a message Apple will always address you by your real name, never by your email address or Dear Customer. Also the sent-from address should be @apple.com or @itunes.com Additionally Apple does not send attachments.

Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams - Apple Support

Forward it as an attachment to reportphishing@apple.com

These bitcoin ransom-ware scams are mass emailed to millions of emails every day. They typically got your email address off the web, or a hacked site. If the password they quote is not current or complete, you have no worries, and having a web site password wouldn’t allow them to do anything to any of your device’s operating systems anyway.

Unfortunately, they are common though and clutter up inboxes. When Sony was hacked, a year or so later my yahoo email was getting one or more a day - my password was not the one they got from the site hack as I’d changed it anyway, but they were annoying as yahoo’s spam filtering is pathetic (I deleted that account long ago now so not an issue).

If you don’t actually use bitcoin or give a wit about it, and your email account or client offers it, make a global rule that any message with the word “bitcoin” anywhere in it just goes to trash.