No e-mails are sent from Easy Redmine
Go to Administration >> Settings >> Email notifications
and verify that the FROM address is correct.
It should be the same (or at least from the same SMTP server) as in configuration file. Otherwise some email services (gmail, yahoo, etc.) may reject notifications.
Check your configuration according to this article in Knowledge base.
To verify that the configuration is correct, try to check if can connect to the mail server from your Easy Redmine server using telnet.
telnet your.domain.here port_number_here (For example: telnet gmail.com 465)
It will show you if you really can connect to your mailserver or there is a problem in your mailserver configuration.