We have a setup of Limesurvey with LDAP authentication and automated user creation.
We use "mail" as the user account so users would log on with "firstname.lastname@domain.com"

Now, when a user logs on the very first time and makes a mistake in the case used to type their email address (eg. Firstname.lastname@domain.com) then the LDAP will return the official full name and the email address HOWEVER the user will be created with the email address with an upper case F instead of lower case...

So, when the user comes back, they try to log in BUT since this time they use the correct email address (firstname.lastname@domain.com - so no upper case F) - the LDAP will return a correct response but Limesurvey will default to the login screen - the user CANNOT access Limesurvey! It is also NOT registered as a 'failed login attempt' in the audit log...