Your MailChimp account can be set up to communicate with Redmine on a per-instance basis. This means that you only need to set up the Integration once with your own account information, and then all your users will have access to the feature. To set up your MailChimp integration, please follow these steps:
1. Get API key
Log into your MailChimp account and navigate to Account Settings > Extras > API Keys.
2. Set API key
In another browser window, log into Redmine using an administrator account, then navigate to your Administration > MailChimp. Paste the key in the API Key text box, then press Apply button
3. Activate Mailchimp module
Navigate to your CRM project Settings > Modules and activate MailChimp module