# Define SMTP Protocol parameters

On Engines, the Simple Mail Transfer Protocol (SMTP) Protocol Agent can be used to redirect connections to a proxy service. On Layer 2 Engines and IPS engines, the Protocol Agent can be used for protocol validation and deep inspection.

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For more details about the product and how to configure features, click Help or press F1.

## Steps

1. In the properties of a custom Service you have created, click Select next to the Protocol field, then select SMTP.
2. (Engine only) On the Protocol Parameters tab, set the parameters for the Protocol Agent.
3. Click OK.