Looks like a malware email has been going out with the envelope from set to firstname.lastname@example.org
The body of the message says simply:
The number varies but seems to be two digits, the attached zip file will be named Invoice#(37).zip where the number will match the one in the body of the email.
The .zip file uncompresses to a file named Invoice_store.exe which contains a trojan.
Details on the malware as analyzed by Virustotal is available here.