Enhanced the user_mail_account and user_transport_account tables by the following fields to track failed authentication attempts and to consequently mark them as disabled:

- disabled TINYINT UNSIGNED NOT NULL DEFAULT 0
- failed_auth_count INT4 UNSIGNED NOT NULL DEFAULT 0
- failed_auth_date BIGINT(64) NOT NULL DEFAULT 0

Associated update task:
com.openexchange.groupware.update.tasks.AddFailedA uthColumnsToMailAccountTablesTask