Two mail servers on the same domain, different and overlapping users. postfix+dovecot and g suite. Is it possible to?

Question

Google Workspace

Good afternoon. I want to purchase g suite to serve a certain number of mailboxes (better not to ask why). At the moment I have a server with dovecot and postfix, which has many mailers and several domains. In g suite I want to add a certain number of users (not all) from the same domain. Accordingly, I have a few questions.
1. If I set up a second mx record, in which the g suite server will be in priority, then how to accept mail for users that do not exist on this server? How to organize it without extra crutches? (Yes, you don’t want to overpay in gsuite for several hundred users who do not need its functionality with the ecosystem).
2. Is it possible to synchronize messages between users that exist in both domains? If possible, how?
3. What pitfalls can be when using this one?

Answer 1

Hello.
Set up Split Shipping - https://support.google.com/a/answer/2685650?hl=en
Thank you