I wouldn't ops check that one. One of the joys of being a PII investigating officer and drafting the 69 page report for the Wg/CC was learning that he NWS (Network Warfare Squadrons?) continually monitor every email leaving the .mil domain, and will quarantine anything that looks suspicious. In the case I had to investigate, the attachments were named something generic, but it was still discovered that they contained SSNs and next-of-kin.
ProTip: When I need to send PII shit out of the .mil domain I just log into my gmail, draft a message, then attach the file. I don't send it, but I can still access the draft and any attachments from anywhere I have access to gmail.