Hi Zentido,
Thanks for dropping by the forum. The double opt-in process is built into the plugin and the MailChimp signup forms, so it can’t be disabled. MailChimp does have an integration with Wufoo, it’s a form building service, that will allow you to create a form with single optin. This page has more info on enabling it: http://wufoo.com/2010/04/13/create-single-and-double-opt-in-forms-for-mailchimp-and-campaign-monitor-integrations/
There are also other integrations in the MailChimp integrations directory that have single opt-in: http://connect.mailchimp.com/
If you have programming knowledge or developers on staff, a single opt-in form can also be created using the MailChimp api: http://apidocs.mailchimp.com/
Have a great day!
