The notification Report Card and logs indicated 100% successful email delivery, but users didn't receive the email message.
All versions of xMatters on Demand
Corporate email solutions with security implementations checking for SPAM and malicious messages
xMatters marks an email as delivered when it has been passed to the downstream provider.
Email domain whitelisting
Corporate e-mail systems often employ DOS sensing due to large volume of incoming messages. To address this issue, consider whitelisting the xMatters email domains.
IP address whitelisting
xMatters does not recommend whitelisting the IP addresses associated with your xMatters service, for the reasons explained here.
The corporate email security system is mistakenly sensing valid traffic as a DOS attack due to high volumes of inbound messaging.