We use Drupal and have a lot of users with more than one email address (but not within the Drupal accounts) - they forget they registered with one email and try to use another to login and failing that, use this other address to create another account. We thus get duplicate accounts.
To add better account information etc to Drupal, i.e. to store proper address details and more than one email address, I thought I would try out CiviCRM.
Last week I set up a local dev environment (Ubuntu 14.04, CiviCRM 5.5.2, Drupal 7.59, PHP5.6.37, MySQL 5.5.61) and synced users. I amended the Name and Address profile to customise it to our requirements and so that users could amend their address details.
I am 100% sure that when I tested someone trying to register through the (now amended) Drupal registration form, it would reject the registration if the email address was already in another field, like 'Other' or 'Home'. I could also login to Drupal with any other the email addresses a CiviCRM user had in their record.
I have rebuilt my environment (to prepare for a pilot) and the duplicate checking and login behaviour has now stopped... I did a demo to a colleague and so I was not dreaming this! I do not remember specifically 'enabling' duplicate checking etc, but it was working exactly as we needed and I was really pleased. It also made logical sense that, as CiviCRM hooks into to the registration screen etc, that somewhere in the background there would be a check on existing email addresses etc.
The other thing I notice is that I am unable to add other email addresses to the Name and Address profile - they just do not display. They do in the user profile (from Drupal) so I am assuming that this is a permissions thing somewhere.
Rebuilding has clearly reset something - does anyone anyone have any ideas as to why this behaviour has changed?