Cloudbric shouldn’t affect your mail server at all, but you need to make sure your MX records are pointing to your mail server. If you are having trouble with your email after activating Cloudbric, then visit here.
For Name server change method, please update all DNS records related to the mail server in your Cloudbric DNS console. Make sure DNS records related to the Mail server points to your original web server.
For A record and CNAME change method, please make sure your DNS records related to the mail server points to your original web server or your mail server in your domain provider's website.