MAil in a box v. 0.43 on ubuntu 18 04 3 does not accept letters, where to dig?

Question

postfix

Good afternoon.
Installed on a clean ubuntu 18.04.3 LTS assembly Mail in a box v. 043 (the last one at the moment according to the script). Sends letters, but does not receive. Firewall disabled, postgrey disabled. Tell me where to dig? Changed nothing, all ports are open. . .
Here is the message from the log:
Sep 23 14:41:10 test postfix/smtpd[12979]: NOQUEUE: reject: RCPT from forward500j.mail.yandex.net[5.45.198.250]: 451 4.3.5 <[email protected]*** *.ru>: Recipient address rejected: Server configuration problem; from=<*****@yandex.ru> to=<[email protected]****.ru> proto=ESMTP helo= accepts
letters between its mailboxes.
I've already disabled everything I can. I just can’t figure out where the letters are hanging and who is hoarding them ...

Answer 1

Reinstalled, it worked.