Connected to localhost.localdomain.
Escape character is '^]'.
220 localhost ESMTP Postfix (Debian/GNU)
250-AUTH LOGIN PLAIN
I tried to go a bit further, by using AUTH PLAIN encryptedpass with a password from perl -MMIME::Base64 -e 'print encode_base64(.....);' and it can successfully authenticate only if the password matches.
So it seems I haven't disabled unauthenticated logins? In that case - how can I fix it?