first pass

Author: forstisabella

src/connections/sources/catalog/libraries/server/http-api/index.md

@@ -3,9 +3,9 @@ title: HTTP API Source
 redirect_from: '/connections/sources/catalog/libraries/server/http/'
 id: iUM16Md8P2
 ---
-The Segment HTTP Tracking API lets you record analytics data from any website or application. The requests hit Segment servers, Segment routes your data to any destination you want.
+The Segment HTTP Tracking API lets you record analytics data from any website or application. The requests hit Segment servers then Segment routes your data to any destination you want.
 
-Segment has native [sources](/docs/connections/sources/) for most use cases (like JavaScript and iOS) that are all built for high-performance and are open-source. But sometimes you may want to send to the HTTP API directly—that's what this reference is for.
+Segment has native [sources](/docs/connections/sources/) for most use cases (like JavaScript and iOS) that are open-source and built for high-performance. But for unsupported use cases, [blocked event forwarding](/docs/protocols/enforce/forward-blocked-events/) or when you're using [Segment-Managed Custom Domain](/docs/connections/sources/custom-domain/), you may want to send data to Segment's HTTP API directly.
 
 > info "HTTP API sources in EU workspaces should use the `events.eu1.segmentapis.com` endpoint"
 > If you are located in the EU and use the `https://api.segment.io/v1/` endpoint, you might not see any errors, but your events will not appear in the Segment app. For more information about regional support, see the [Source Regional support](/docs/guides/regional-segment/#source-regional-support) documentation. 
@@ -16,6 +16,8 @@ Segment has native [sources](/docs/connections/sources/) for most use cases (lik
 
 Choose between [writeKey authentication](#writeKey-authentication), [basic authentication](#basic-authentication) and [OAuth](#oauth) to authenticate requests. 
 
+When authenticating with the HTTP API, don't hard code the IP addresses used to invoke the API. You should refresh this IP address at least once a day or when you experience [5xx errors](#experiencing-5xx-errors). 
+
 #### writeKey authentication
 Authenticate to the Tracking API by sending your project's **Write Key** along with a request.
 The authentication writeKey should be sent as part of the body of the request. This will be encrypted over https.
@@ -284,7 +286,7 @@ Find more details about Group including the **Group payload** in the [Segment Sp
 
 ## Alias
 
-`Alias is how you associate one identity with another. This is an advanced method, but it is required to manage user identities successfully in *some* of Segment's destinations.
+Alias is how you associate one identity with another. This is an advanced method, but it is required to manage user identities successfully in *some* of Segment's destinations.
 
 In [Mixpanel](/docs/connections/destinations/catalog/mixpanel/#alias) it's used to associate an anonymous user with an identified user once they sign up. For [Kissmetrics](/docs/connections/destinations/catalog/kissmetrics/#alias), if your user switches IDs, you can use 'alias' to rename the 'userId'.
 
@@ -481,4 +483,8 @@ Segment welcomes feedback on API responses and error messages. [Reach out to sup
 
 1. Double check that you've set up the library correctly.
 
-2. Make sure that you're calling a Segment API method after the library is successfully installed—[Identify](#identify), [Track](#track), and so on.
+2. Make sure that you're calling a Segment API method after the library is successfully installed: [Identify](#identify), [Track](#track), and so on.
+
+### Experiencing `5xx` errors
+
+If you're experiencing `5xx` errors, refresh the IP address you use to invoke Segment's HTTP API.