From a letter I received from the Ombudsman today. Names have been omitted to protect the repentant:
[Department] has acknowledged the failure to meet its obligations under the OIA in this case and expressed regret for the delay. It has advised me that your request was not received by a person at [Department], as a combination of words used in the email meant that it was quarantined as a possible phishing scam...And this was for a request for OIA stats (dubious words: "performance", "Excel"). Cthulhu only knows what will happen if I try asking Pharmac about whether it subsidises anti-impotence medication, or MFAT about relations with Nigeria, or Internal Affairs about common types of spam.
The good news is that saying "we didn't receive it" doesn't get a department off the hook. The Ombudsman takes the view that email is received by a department the moment it hits the server (something which a few Ministerial staffers need to learn as well). This department agrees, and is refining its software so it doesn't lose requests in future.