[exim] smtp authenticators do domain auto qualify??

Hello!

I have a strange problem with plaintext authenticators. It looks like auto
domain qualify. Authenticator configuration:

PLAIN:
  driver                     = plaintext
  server_set_id              = $auth2
  server_prompts             = :
  server_condition           = ${lookup mysql{........
#  server_advertise_condition = ${if def:tls_cipher }

As I use virtual domains, users are authenticated useing username@domain.
So, when user is authenticated I'm getting log entries like:
1LSq7S-000Nki-Ew <= "boris@??? H=([127.0.0.1])
[80.64.29.123] I=[80.64.16.35]:25 P=esmtpsa X=TLSv1:AES256-SHA:256
A=PLAIN:boris@??? S=725 id=4982CEE9.5060808@??? from
<boris@???> for boris@???

"boris@??? - confuses me. When I remove qualify_domain
options the string changes to
"boris@??? where the mail.tagnet.ru is the primary
hostname. Is there a way to disable qualifying? Exim 4.69