Hello. The system does not send email confirmations to customers and administrators since upgrade backend. All settings are ok. There are no emails in spam too.

Hi Max,
your email server does not accept messages from our server. You should contact their support.
Here is the error message from our logs:

EMAILmax-tm@mail.ruREASON550 5.7.1 This message was not accepted due to domain (mail.ru) owner DMARC policy (RFC 7489) https://help.mail.ru/mail-help/postmaster/dmarc SMTP-ID<eb9426916d24d9209cc8f179c3ef3037@booking.drivenot.com>PROCESSED STRINGApril 9, 2017 - 04:56:31 AMMSGIDLJaYKEowRveByqwqlj-_kg.filter0460p1mdw1-30186-58E9B0EB-2A.0

Hope this helps.
Kind regards.

What about email info@transfer24.kz? I make all orders to that email. There are no confirmation too. Why everything was ok before you upgrade backend?

There are no logs for email info@transfer24.kz in our email log at all.
There are logs for user@transfer24.kz and all emails are delivered and opened on the other side.

Update of the back end is just a coincidence here, it is just a design update and did not affect any functionality connected with emails.

Hope this helps.
Kind regards.