Email templates & campaigns

How are the email templates used? I do not see how one can use an email template to send to leads, prospects, accounts, etc?

Also, on the campaigns, is there a way to set up an external mailbox that ZOHO CRM can check for sales inquiries? (sort of the way ServiceDesk checks for requests).

I'd like to use marketing sources to get leads directly into the system. Preferably, I'd like them to come via emails sent to "sales@company.com". The leads would go into an unassigned lead farm.