Mailchimp is a email list service that allows you to send messages to your customers in an easy to use interface. PHP Point Of Sale integrates with mailchimp by allowing you to add customers, suppliers, and employees to your mailchimp lists.

Here are the steps to integrate with PHP Point of Sale:

1. Login to mailchimp

2. Click on the left side your username

3. Click Account on the menu that appears

4. Click Extras

5. Click API keys

6. Generate a key

7. Copy the key (CTRL + C)

8. Open PHP Point Of Sale

9. Click Locations

10. Edit the location you want to add the api key to

11. Paste (CTRL + V) the API key into the "Mailchimp API key" field and hit submit

Learn more about mailchimp integrations at:
https://mailchimp.com/integrations/