We can confirm that the emails are not being filtered as spam and do not appear to be hitting our email server.
From looking at header.pl within the iDrive install files it is noted that the email alert requests are sent to URL ‘https://webdav.ibackup.com/cgi-bin/Notify_email_ibl' to be generated and sent out from your side. Can you see the requests hit this URL in the first instance?