wp_ajax_wp_block_form_email_submit

See hook in action

See this hook used in plugins:

Select Plugingutenberg.16.9.0gutenberg.17.0.2gutenberg.17.1.2gutenberg.17.2.3gutenberg.17.3.0gutenberg.17.4.1gutenberg.17.5.0gutenberg.17.5.2gutenberg.17.6.5gutenberg.17.7.0gutenberg.17.8.0gutenberg.17.8.2gutenberg.17.9.0gutenberg.18.2.0gutenberg.18.5.0gutenberg.18.6.1gutenberg.18.7.1gutenberg.18.9.0gutenberg.19.0.0gutenberg.19.1.0gutenberg.19.2.0gutenberg.19.4.0gutenberg.19.6.1gutenberg.19.6.4