Hi All, This is my first message. I bought today a subscription for the next 6 months as I think that this project really worth it, and I would like to support it as much as I can. One week ago, I've installed ISPConfig in a new Debian's (Jessie) server following every step explained on the guide "The Perfect Server – Debian 8 Jessie (Apache2, BIND, Dovecot, ISPConfig 3)", located at https://www.howtoforge.com/tutorial/perfect-server-debian-8-jessie-apache-bind-dovecot-ispconfig-3/ All was installed without any problem nor error, and seems to work flawlessly except one thing related with the incoming mail. Unfortunately I am getting the error message "User unknown in virtual alias table" everytime I try to send an email from other mail servers external to the ISPConfig server. I've been testing with differents email providers to be sure that the problem is on the ISPConfig server side. On the other hand, ISPConfig sends perfectly any email message to others email accounts located outside him, so the problem is happening only in one direction: from outside to the ISPconfig server. So, I downloaded and searched in the ISPConfig Manual about how to solve that behaviour but I haven't found any other step to do when you add a domain and an account for the mail service (apart the ones I've done by myself and that are explained in the documentation with screenshots too). Prior to create this thread, I've searched on the ISPConfig's forums too, and I find the explanations a bit confusing. Till, Falko, and other experienced users gave help to others like me which had the same problem, but they mentioned some Postfix configuration files which are not cited on the HowToForge's guide, nor in the ISPConfig Manual either. I'm talking about a couple of files called "/etc/postfix/virtusertable" and "/etc/postfix/local-host-names", which at least in the 18.104.22.168p8 release they didn't exist. I don't know if I have to create them from scratch, or if it is not necesary to do that anymore, because the data are now stored in a MySQL/MariaDB database, and that kind of configuration/modifications is done now automagically by the web administration panel... I don't know. As you can see, I'm a bit lost. I will be very appreciated if somebody could help me with this issue that is hammering my brain since 3 days ago. Could somebody help me, please? Thank you very much in advance!!