Problem
You have set up the Exalate notifications in your node, but no notifications are sent.
Cause
Currently, Mimecast (and maybe other mail servers) are bouncing emails from mail.com due to an unknown reason.
Please make sure that emails from exalate.com are not being bounced.
Solution
Configure the 'permitted senders' option on your mail server.
In the case of Mimecast - check the following document
https://community.mimecast.com/s/article/Configuring-Permitted-Senders-Policies-1067720131