Thanks, @Muse. I typically trash these types of things, but have never gotten one like this. Looking at the header of the email, it was sent from

flpd591.prodigy.net

with the IP address 194.69.248.230 which traces to Spain (explaining the broken English in the email).

I did a quick visual of my site contents via FTP and nothing looked unusual, but I'll do as you suggest and run a malware scan.

Thanks again.