Please note: The hotfix packages do not supply the upgrade procedure. If you want to upgrade to a newer version, you can download the upgrade package from
here and then apply hotfix for particular version.
EmailProvider – e-mails with non-existing addresses were processed by SMTP server despite of relay restrictions; this issue was caused by ‘SmtpClient.UseDefaultCredentials = true’; the property may be set by new app settings key ‘CMSEmailUseDefaultCredentials’ now.
Found in version 4.1, status: fixed, date: 11/2/2009