> For the complete documentation index, see [llms.txt](https://docs.reach-book.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.reach-book.com/integrations/customer-database.md).

# Customer database

Connect your own customer database so Reach-book.com can check whether a prospect is already a customer before you email them. Existing customers aren't sent follow-ups.

![The Customer database connection settings](https://965745608-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fdg7LyestsaNAIIzzILlv%2Fuploads%2Fgit-blob-6d5fe7d07acc754b7d3331237691df3e1fa8eedc%2Fcustomer-database.webp?alt=media)

Open **Workspace settings → Customer database**. It has three tabs.

## Connection

* An HTTPS lookup URL
* GET or POST
* Authentication: none, bearer token, or an API key header
* A request template using `{{email}}` and `{{domain}}`

## Mapping

Tell Reach-book.com which part of your system's response means "this is a customer".

## Test

Click **Run a lookup** to try it with a real email.

Turn **Automatic checks** on to check new prospects automatically. Saving the connection runs earlier customer checks again. You can also check selected prospects with **Check customers** on the prospect list.