E-mail settings are located in Site Manager -> Settings -> E-mails. Among other e-mail related settings, these settings are related to the e-mail queue:

 

Enable e-mail queue - if checked, e-mail queue will be used while sending e-mails.

Archive e-mails (days) - number of days for that will e-mails sent via e-mail queue remain stored on the Sent e-mails tab

 

 

Page url: http://devnet.kentico.com/docs/devguide/index.html?email_queue_settings.htm