Thanks folks for your comments here. This letter was sent to us twice in the span of ~4 hours, once as normal email and another time as attachment file.
Good to see that a lot of people are waking up to the truth about Islam. Yet, we need more enlightened people about Islam and we need them quickly. Else we are all doomed even here in the West for an alien cult.
"This letter was sent to us twice in the span of ~4 hours, once as normal email and another time as attachment file."
If you had included the email header, the email threat might actually be traceable and actionable, since you include the supposed senders address. If it was forged, it might be obvious, since the path would be missing or wrong.
If it does not contain a valid header, there is a good possibility it was created and sent by someone who's purpose was to sucker well-meaning people into sending nasty-grams to that address - stiring up more trouble.
A good idea also would be to include actual scans of the original posted flyer threats on your pages.