Update index.md

Author: Panandhan22

src/connections/destinations/catalog/iterable/index.md

@@ -24,6 +24,8 @@ When you call `identify` with one of Segment's sources, Segment calls Iterable's
 
 Iterable keys users by `email` or a user ID. This user ID will be the Segment `userId` if sent. To use a Segment `userId` for identify calls, first call identify with both a `userId` and `email`. Iterable won't accept the request and throws an error if you fail to send one of either the `userId` or `email`.
 
+**NOTE**: Email parameter has to be passed only as the `email`, email value can't be passed as some other parameter in payload as it can't be detected by Iterable. The same applies for user ID parameter, it has to be passed as `userId` in payload. For example, you can't pass the `email` and `userId` as "mail" and "id" in event payload. This will be silently rejected by Iterable.
+
 <!-- commented out because this functionality isn't currently working ZD#355518
 ### Merge Nested Objects
 
@@ -58,6 +60,8 @@ When you call `track` with one of Segment's sources, Segment calls Iterable's [t
 
 If a user does not already exist in Iterable, calling `track` for a user event will add that user into the system. You can track with either an `email` or userId (if a `userId` exists for that email).
 
+**NOTE**: Email parameter has to be passed only as the `email`, email value can't be passed as some other parameter in payload as it can't be detected by Iterable. The same applies for user ID parameter, it has to be passed as `userId` in payload. For example, you can't pass the `email` and `userId` as "mail" and "id" in event payload. This will be silently rejected by Iterable.
+
 ### Example steps:
 
 First `track` event with `userId` and `email`; user will be created