Using a local IIS SMTP gateway is strongly recommended to improve performance. A local SMTP gateway is configured to forward emails to the enterprise SMTP gateway ("smart host") only, so the current enterprise security will be applied.
There are several advantages to using an SMTP relay at the IIS WorkflowGen server:
Better performance, since messages are sent directly to the relay.
Local SMTP acts as a buffer to avoid loss of emails if the main SMTP server is not available.
Connection problems are reduced because the relay manages communication problems.
The relay traces email deliveries in its own log files.
The relay allows you to limit access to WorkflowGen.
The relay supports SMTP authentication and encryption (TLS encryption) to connect to your Exchange SMTP (or other mail server).
Configuring an IIS SMTP gateway
Make sure the SMTP service is installed on the Windows server used as the SMTP gateway.
In IIS, edit the properties of the Default SMTP virtual server.
On the Access tab, click Relay.
Click the All except the list below radio button.
Click Apply and close this window. (For an increased security level, grant access only to the web server IP.)
On the Delivery tab, click the Advanced button.
In the Smart host field, enter your SMTP gateway address (IP or hostname).
Using a pickup directory
Alternatively, WorkflowGen also supports pickup directories. Notifications are created in a pickup directory managed by the SMTP server. The path to the pickup directory is set in the SMTP section on the General tab in the Administration Module Configuration Panel. (Alternately, you can set the path to the pickup directory as the value of the ApplicationSmtpPickupDirectory parameter in the WorkflowGen web.config file.) The default pickup directory path is C:\inetpub\mailroot\Pickup.
Once you've properly configured the pickup directory in WorkflowGen, you need to configure your external SMTP service (such as IIS SMTP Server or Exchange) to process the emails that are created by WorkflowGen in the pickup directory.