Undelivered Mail Returned to Sender

This is the Postfix program at host email.orsk-adm.ru.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The Postfix program

<linuxdd@orsk-adm.ru>: host web.orsk-adm.ru[83.146.112.30] said: 554 Mail for
[email]linuxdd@orsk-adm.ru[/email] rejected for policy reasons. (in reply to RCPT TO
command)