Email addresses are case sensitive

[jace]

Email addresses are case sensitive

[jace]

Possible solution to the second problem with Gravatar, etc: store two normalised emails:

1. Lowercase normalised version, which has a unique constraint (in UserEmail only). This is the reference for queries. It could be the existing LOWER(email) index instead of a distinct column.

2. Application normalised version in which:

   1. + suffixes are removed,
   2. @googlemail.com is replaced with @gmail.com (ref), and
   3. periods are stripped from @gmail.com addresses

The application normalised version is used for discovery of a re-used email address, but uniqueness is not enforced, since there are legitimate reasons for users to re-use addresses. It may be used for relevant security checks if, for example, one version is used as a user's email address and another as a organisation's or team's, to warn the user that shared access to the email address may compromise their own account.

[jace]

The logic for application normalised emails could be in the mxsniff library, although that one currently involves a DNS lookup. mxsniff's provider list could be modified to include the primary domain instead of the MX target, and a custom normalisation function.