iMIS 2017, and iMIS 20.3 environments.
The above has been reported multiple times, and all of the times that this has been reported so far, it has been related to the lack or absence of not having a SPF DNS Record the sending email address' domain.
In order to resolve this concern, please ensure to verify if your iMIS App server's sending IP address has been added to your SPF Record.
1) There are multiple sites where this can be checked. One of the most popular DNS Query sites is known as MXToolBox: www.mxtoolbox.com
Sample Query Image:
2) Ensure that your sending public IP Address is listed in the SPF Record. If your public IP Address is not listed, please sign in to your DNS portal (DNS hosting) and add the SPF Record. Or contact your domain DNS hosting company for assistance in how to add the SPF Record, they should be able to assist with this typical request.
3) Also, if you email is being used in the CC, or BCC field in your iMIS Communication Template, please ensure that your iMIS Sending IP address is also added on your company's email White List, and the sending email address would also be a good practice. Since you may be receiving a bulk of emails coming from your iMIS Communication Suite, and not from your company's mail server, there could be a possibility that those emails may be rejected, or catch by your own anti-spam filtering solution.
4) Once the SPF DNS record has been fully updated, you should be able to test again, and confirm that you are receiving the emails been address to you via the Carbon Copied (CC), or Blind Carbon Copied (BCC).