An English string is harcoded in http://mxr.mozilla.org/bugzilla/source/Bugzilla/Config/Auth.pm#116 . As a result, this string appears in English in parameter emailregexpdesc in the administration interface on localized installations. This string should be localizable.
We are going to branch for Bugzilla 4.4 next week and this bug is either too invasive to be accepted for 4.4 at this point or shows no recent activity. The target milestone is reset and will be set again *only* when a patch is attached and approved. I ask the assignee to reassign the bug to the default assignee if you don't plan to work on this bug in the near future, to make it clearer which bugs should be fixed by someone else.