I have described several configuration issues in the FAQ.pdf.

E.g. Joomla framework does not send emails when the senders address is not valid. When you have configured an invalid address in uddeIM, other components may use hard coded addresses, uddeIM will not send emails, the other components do.

There are some other issues, please check the FAQ.

From the FAQ:

10.3 Email notifications
10.3.1 E-Mail notifications are not sent
uddeIM does not send any email notifications, what's wrong?
There are a lot of issues which could cause this problem:
- Check if "Email stop" is still activated in backend (it is activated by default after a fresh installation of uddeIM).
- Check if you have enabled email notifications in backend (use "yes" when all users should be notified or "admin" when admins should be notified only).
- Check if you have set "Default email notifications" to "always". This is the default for the users’ frontend setting. Existing user settings are not changed; this is used for new users only.
- Check if the user has enabled email notifications in frontend (you can do this using the backend "userlist settings").
- Check if the emails are not filtered by your or the recipient's ISP. When you are not using a smarthost sometimes it happens that your email server is on a remote blacklist which means the emails are sent but filtered.
- Check the mail settings in uddeIM and Joomla:
Usually "phpMail" should be the correct setting in uddeIM. This requires that PHP is correctly configured so it can send emails using the PHP command "mail". If you have problems you can try "mosMail" which uses a Joomla library function to send emails. This requires that Joomla is correctly installed and the mail system is configured correctly.
- You have to configure “mosMail” when you have configured “SMTP” or “Sendmail” in Joomla.
When “mosMail” is used, check if you have configured the full “E-mail sender address”. Default is “webmaster” which does not work on most systems, so you have to configure “webmaster@yoursite.com”. So when your site is “www.myclan.org” use “webmaster@myclan.org” (or another valid email address).
When “phpMail” is used, check if you have entered values for “E-mail sender name” (e.g. “Messaging”) and “E-mail sender address” (e.g. “webmaster”). Without valid settings PHP does not send any emails.
- Some providers require that you use a known email address – an email address that already exists on your web space - when you send messages using phpMail.

...and some more...