ICANN's IDN report: 29% of tested mail servers accept internationalized addresses

ICANN’s IDN Implementation and UA Adoption Report 2026, dated September 1 and covered by CircleID on September 23, counts 151 delegated IDN top-level domains in 37 languages and 23 scripts as of June, and about 4.3 million IDN registrations at the second level. Roughly 71% of those sit under ccTLDs; .рф leads with 779,000. IDN registrations under gTLDs fell 2.65% year on year to 1.359 million at the end of March 2026, down from 1.518 million in December 2022.

Acceptance is still the gap. The share of tested gTLD mail servers supporting Email Address Internationalization rose from about 20% in 2022 to 29% in 2026. An automated test of 923 websites found 20.6% accepted an internationalized email address, against 11.1% in a 2025 survey of 2,000 sites run a different way. THNIC’s test of 220 Thai websites found 4.5% of registration forms accepted a Thai-script email address.

The report also carries ICANN’s February analysis of reputation block lists from October 2023 to September 2025. ASCII names were reported at 5.3 times the rate of IDNs, and phishing was the top threat type for both. The most-reported IDNs were Latin script, at 0.26% of all Latin-script IDNs.

Browsers and mail filters restrict IDNs mainly on homograph risk. In ICANN’s block-list data, IDNs are reported at under a fifth the rate of ASCII names.