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+Properties can be set in a node or in an incoming message to define behaviour. 
+
+For example, when using a file node, either setting 'Filename' in the node or setting `msg.filename` in an incoming message will read from that file. If both properties are set `msg.filename` will currently override the node property.
+
+This behaviour is only found in some nodes and can have unexpected consequences as described in this [issue](https://github.com/node-red/node-red/issues/399). Therefore, message overriding has been deprecated. In future nodes and future releases `msg.some_property` will only be used if the property is not set in the node. Nodes currently using the override functionality will continue to function in this release but will also receive a warning noting that this behaviour is deprecated.
+
+The core nodes and properties affected by this behaviour are:
+* **http request:** `msg.url` and `msg.method`
+* **email:** `msg.to`
+* **file:** `msg.filename`
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