Because this information could be invisible for most, I thought I post it here again.
The on-site-notifications plugin informs your user about private messages now! Including a preview of the message:
If you like the plugin and you like more features (such as notifications for wall posts), please consider a donation. Find out more about the plugin donations here on question2answer.
For issues / bugs, please report them at https://github.com/q2apro/q2apro-on-site-notifications/ or as comment at http://www.q2apro.com/plugins/on-site-notifications
For ideas, feel free to comment / answer below.
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.