Does it sound like this email has really come from Royal Mail?

[me]

I received an email from Royal Mail today (or at least it said it was from Royal Mail), The email told me that they have detained my package, and the RM International Mail Branch will write to me telling me why it has been detained and how I can get it released.

There was a file attached, but when I tried to open it, this message came up on my antivirus software (avast! File System Shield has blocked a threat. No further action is required)

I looked on the internet to see what was happening, and I found this web page (below).

http://blog.mxlab.eu/2013/12/04/newer-ve...d-package/

My email is exactly like the example on this website (apart from in the subject on my email it says "ATTN: Lost / Missing package" instead of "Warning: Lost/Missing package"

The email address it was sent from was bpotbmdow@jazfry.com, which to me doesn't sound like a Royal Mail address. The reason I'm wondering whether it really did come from Royal Mail, is because I am expecting a package to be delivered by them anytime soon.

What should I do about this?

Thanks for help.
The second answer is right, how could they have got my address and know that I've placed an order for something? Should I report this to someone, and who should I report it to?