There is no core Discourse feature to send posts only from users on a specific domain (e.g., gmail.com) to the review queue.
The closest related feature is the auto approve email domains site setting, which allows certain email domains to bypass the manual user approval process by automatically approving users from those domains.
There are also settings for blocked email domains and allowed email domains that provide a way to restrict or control who can register on your site based on their email domains:
However, these settings would all require the must approve users setting to be enabled, and only impact users initially registering on a site, and not the interaction between creating posts and the review queue.
As a workaround, you could use Groups to accomplish a similar functionality though. For example, you could create a custom group and automatically add users who register with a specific email address to the group, and then add this group to the approve unless allowed groups and approve new topics unless allowed groups setting.
With this type of setup, you could effectively bypass the review queue for users with a specific domain, while still sending other posts to the review queue if desired.