It's reasonable to expect that phishing emails that come to your inbox will be in your native tongue.
That may be the case for many, but not for all. And differing languages presents a challenge for email security layers.
Consider this email that Proofpoint missed.
This email is in French. It's a fairly simple credential harvesting scheme.
The subject, in English, reads: Update
The text, roughly translated in English, reads: "Sorry, for more security we ask you to identify yourself in order to avoid the deletion of your account."
Should you click on the hyperlink, you'll be directed to this credential harvesting page:
True anti-phishing protection will be able to detect schemes in all languages. That's what Avanan does.