Make Profile Double-opt process configurable

By default, joining (subscribing to) a group via a Profile form requires double-optin (user get's a confirmation email) IF the CiviMail component is enabled. This means that profiles which include the "Group(s)" field must also include an Email Address field.

(This also means that Drupal and Standalone sites should enable the permission to "access CiviMail subscribe / unsubscribe pages" for anonymous role if visitors are going to sign up for mailing lists via profile).

To over-ride this behavior (eliminate the double opt-in requirements) - add the following line the your site's civicrm.settings.php file:

define( 'CIVICRM_PROFILE_DOUBLE_OPTIN' , 0 );