You can choose from hundreds of integrations. You can use them as they are or customize them to suit your needs.
Every time someone subscribes to a Mailchimp list, Integromat will automatically send him/her a welcome message.
Every time you add a certain label to an email in Gmail, Integromat will check if a subscriber with the sender's email address already exists in MailChimp. If not, Integromat will create a new subscriber in a MailChimp list of your choice.