A domain that looks like but isn't where the actual characters are different. Internationalized domain names (IDN) let browsers render non-Latin scripts, Cyrillic, Greek, Cyrillic lookalikes for Latin letters. а Cyrillic "а" (U+0430) looks pixel-identical to a Latin "a" in most fonts. so does Cyrillic "е," "о," "р," "с," "у," "х." register "аррӏе.com" using Cyrillic characters, and browsers that support IDN will render it as in the address bar. underneath, the actual domain is punycode, the ASCII-safe encoding browsers convert IDNs into. you never see the punycode. you see so does your email client. so does the padlock. a researcher demonstrated this against Chrome and Firefox in 2017 using exactly that spoof, and both browsers rendered it clean. the fix isn't "look closely." you can't. it's browsers flagging mixed-script domains, and you checking the punycode directly when something feels off.