dovecot 2.x doesn't work with @domain1.org authentication

Question

cat /etc/dovecot/conf.f/10-auth.conf

[...]
disable_plaintext_auth = no
auth_username_format = %n-AT-%d
[...]

or also using %u variable (full username (e.g. user@domain)

cat /etc/dovecot/conf.f/auth-passwdfile.conf.ext [...]

passdb {
  driver = passwd-file
  args = scheme=SHA256 username_format=%n /etc/dovecot/users
}

userdb {
  driver = passwd-file
  args = scheme=SHA256 username_format=%n /etc/dovecot/users
}

cat users

info@domain1.com:{SSHA256}wr4SgH6sH5hNrSQhbVX/zUQqJrmO63aYI9Ograx+N0gZ1lAG
[...]

cat /var/log/dovecot.info

Aug 18 16:56:22 auth: Debug: passwd-file(domain1_info,192.168.50.212,<cGn/VAhX9YrAqDLU>): lookup: user=domain1.org_info file=/etc/dovecot/users                                                                                                                                                                                                                             ==> /var/log/dovecot.info <==                                                                                                                                                                Aug 18 16:56:22 auth: Info: passwd-file(domain1_info,192.168.50.212,<cGn/VAhX9YrAqDLU>): unknown user (given password: test)                                                                                                                                                                                                                                                     ==> /var/log/dovecot.debug <==                                                                                                                                                               Aug 18 16:56:24 auth: Debug: client passdb out: FAIL    1       user=domain1.org_info      original_user=info@domain1.org                                                          Aug 18 16:56:24 pop3-login: Debug: Ignoring unknown passdb extra field: original_user
[...]

I'd like connect to dovecot using username@domainX.org because if I modify

/etc/dovecot/users

removing the domain after username, dovecot accepts username authentication