Sometimes it’s important to know, if the user should have received the email notification generated by Redmine. Especially, if usage of Redmine in your organization relies on email integration (for example, if it’s configured to receive user comments, such as issue notes and message replies, via email). In such cases, some users may use Redmine user interface very rarely as all the communication can be made through emails.
Until now it was impossible to determine using Redmine, if the particular email notification was sent to the particular user. For this, you would need to dig into the logs of the message transfer agent (MTA) (if you had access to those logs, of course). Even so, it was not easy to link records in such logs to certain email notifications.