I found that there is an option in the GitLab to send e-mails to users:
Project -> Settings -> Integrations -> Project services -> Emails on push
Project -> Settings -> Integrations -> Project services -> Pipelines emails
But it's not the case: one should provide the list of recipients, track incoming and out-coming users etc.
Is it possible to send e-mails to all group members without manually modifying this list?
Thank you and best regards.