Migration from gmail to exchange how to implement?

Question

gmail

There is a certain domain that is delegated to google, more precisely, only mx records. All mail immediately comes to google servers, from where it is picked up by clients. There is a task - to transfer all this to exchange. Exchange was raised (at the moment, almost the latest 2016 cu12), the domain was added as serviced with internal forwarding (internal relay), the send connector was also configured, it sends all mail that comes to the exchange server, but does not find the recipient, to google servers. This was done in order to gradually transfer people from google to exchange, this migration option on the Internet is called coexistence.
Case:
1. There is a user [email protected], his account exists only on the google server.
2. A letter is sent to the user [email protected], it arrives at the exchange server, the recipient with that name is not found there.
3. The exchange server forwards it to the google servers using a special send connector.
Subject:
If you send letters from mail domains, such as yandex.ru, gmail.com or your own exchange, then the letter comes to the addressee [email protected]
If you do the same operation with mail.ru, then a bounce comes and the mail does not reach. In send connector logs:
<,550 5.7.1 Unauthenticated email from mail.ru is not accepted due to domain's DMARC policy. Please contact the administrator of mail.ru domain if this was a legitimate mail. Please visit https://support.google.com/mail/answer/2451690to learn about the DMARC initiative. w1si11772712pgj.113 - gsmtp,
That is, mail.ru forbids redirecting its mail and nothing can be done about it?
I read an article on Habré, in which nothing but "understand and forgive" in my case is not suitable.
The option to install exchange behind google servers also does not work, since there is an old free account in which such functionality is not supported.

Answer 1

you are better off on LOR or opennet
for example, how error 251, 252, etc. is handled.

Answer 2

a year ago, I migrated from sweb servers to my exchange server
in stages:
1) We raise our exchange, configure it to receive and send letters, exclude Google servers from the email delivery chain
2) download all user letters from Google servers (there are a lot of scripts on the network for this subject, pump out all letters, attachments, drafts, etc.)
3) fill in all letters from users to them in boxes
25 boxes were transferred in a couple of days

Answer 3

The problem is that with the current settings, your forwarding is organized in such a way that it changes the contents of the letter, which leads to a violation of the DKIM signature. Because of this, GMail does not accept emails from any domains with strict DMARC, incl. from mail.ru.
You can try to organize the redirect in such a way that it does not change the email and does not violate DKIM. You can try to do this using the connector settings in Exchange so that the forwarding does not change the message format, or you can set a separate host as a gateway between Exchange and the external network, I would recommend doing this anyway, because. Exchange does not support DKIM/DMARC.

Answer 4

Something I have doubts that mail is sent from mail.ru servers.
You can confirm - go directly to the mail.ru box -> and send an email to the user [email protected] from the web interface.
PS
Just DKIM from mail.ru protects the fields: Content-Type:Message-ID:Reply-To:Date:MIME-Version:Subject:To:From
None of them changes during the transfer.

Answer 5

And no one set up the parallel work of gmail and echchange?
I have conditionally corp.ru on gmail and corp.org on chang. Is it possible that both there and there were the same users and they would have duplicate letters?