Hi,
Unfortunately, there's not enough information in this email to help you. You should check for error in your DSpace logs, see
https://wiki.lyrasis.org/display/DSPACE/Troubleshoot+an+error#Troubleshootanerror-DSpace7.x(orabove) If there are no errors in the DSpace logs, then we'd need more information on whether the email is received by users or not. If it is *not* received, and there are no errors in the DSpace logs, that would imply either an issue with your Email Server, or that the email was caught up in Spam filters. Unfortunately, if it's an issue with the Email Server, then that is an issue outside of the DSpace software itself, and you'd need to check your Email Server documentation/logs to see if you can figure out why it won't accept emails sent from DSpace.
Good luck and let us know on this email list what you find.
Tim