In Crelate, you'll see the option to "Send Email" in addition to "Start Campaign." There are several differences here that will be noted below.
Send Email: For the "Send Email" option, this will come directly from your email server. Therefore, when sending a message, you may send in bulk with no BCC or CC to a group of candidates. This email, as a result of coming from your email server, will show directly in your sent email folder. These emails will NOT have the option to track open rates, click rates, etc through Crelate's Campaign function.
Start Campaign: For the "Start Campaign" option, these emails will come from your email address but from Crelate's email server. Meaning, you will not see these emails in your sent box but will be able to track open rates, click rates, etc as a result of these emails being sent from Crelate's email server. Similar to the above, there is no CC or BCC with this option.