The server1.example.com point to 192.168.0.174. I did as instruction by putting 192.168.0.174 server1.example.com server1 in /etc/hosts file. I don't know what else needs to be done? I still can access only by IP address only. In ISPConfig, I clicked Email, added domain called server1.example.com, Domain example.com, spamfilter not enabled. Then, I added a mailbox for falko, real name Falko, email firstname.lastname@example.org
, password falko, Quata 10MB, sent copy to is blank, spamfilter not enabled, Enable Receiving box is checked, Disable IMAP and Disable POP3 boxes are unchecked and saved it. I still get Unknown user or password incorrect error message when I tried to login. Thank you for reply in advanced.