It is impossible to authenticate with a idn domain when using SQL authentication if domain are stored in punycode:

exemple test mailbox edvil@ëdvil.fr

SOGO request the following to authenticate :
SQL: SELECT c_password FROM sogov WHERE c_uid = 'edvil@ëdvil.fr';

which returns nothing because domain is punycoded.

The right request should be:
SELECT c_password FROM sogov WHERE c_uid = 'edvil@'xn--dvil-kpa.fr';

Using punycoded domain to log in works.

Imho, there should be an option in sogo to encode/decode idn domains to/from punycode in sogo.conf.