Add information about sending to a Segment source

Author: spencerattick

src/connections/functions/destination-functions.md

@@ -433,6 +433,9 @@ If you're sending your batch to an external service, the execution time of the f
 
 {% include content/ip-allowlist.md %}
 
+##### Can I use a Destination Function to send data to another Segment source?
+Sure! If you do this, please remove the `messageId` and the `writeKey` from the payload in your Function code. Leaving either field on your payload will cause unexpected behavior that may cause your event to be delivered to the wrong source or to not be delivered at all. 
+
 ##### Can I view console.log() outputs in Destination Functions?
 
 Incorporating console.log() statements in your Destination Function code aids in debugging. However, logs generated by these statements will only be accessible in the [Event Delivery](/docs/connections/event-delivery/) view if the payloads encounter errors during processing. Logs from successfully processed payloads are not displayed.