Not sure if this is what is going on with you or if it is a bug or normal operation of cforms 2 but here is the email situation I have found on my set up. I am using cforms in conjunction with a CRM. The emails with in the cforms 2 setup work perfectly for me as well as the data base tracking/logging. That is of course until I set up the form to push the info to the CRM to collect. Once the CRM hooks are set, the emails as well as the database tracking/logging no longer works within cforms 2 itself. So instead I have to send emails to myself and people submitting forms emails from the CRM. This is not a big deal but I really would like to receive an email from the cforms 2 plugin as well as my CRM so I know if something is not working.
Again, I’m not sure of you set up but maybe this will help. Also try try turning on logging and tracking or whatever it is called in the global settings. Also, like postman is saying, I think, Gmail and some other large email services don’t like sending out automated emails in my experience. Hope this helps.