Hi @gine001,
Which of our applications are you using, and what version? (Please include this information with your posts.)
The most common cause of emails not being received is that the delivery service is marking them as spam. First ensure that your email configuration is correct – e.g. the settings in config.inc.php. Then, if delivery is still problematic, see if you can access your mail server’s sending logs. This is the only sure way to know why the server is rejecting the messages. Commonly it’ll be something like DMARC rules (there are useful threads on this elsewhere in the forum).
Regards,
Alec Smecher
Public Knowledge Project Team