Today i found out that on one of my servers, i can not establish a connection via IMAP. The portscanner within the ISPConfig (on the server itself), shows that the following IMAP ports are open: Port 143 (tcp) is open (imap2)! Port 993 (tcp) is open (imaps)! netstat -tap | grep imap shows me: tcp6 0 0 *:imaps *:* LISTEN 1980/couriertcpd tcp6 0 0 *:imap2 *:* LISTEN 1968/couriertcpd But when i try to establish a connection via telnet from my local desktop with: telnet 18.104.22.1689 143 It fails... The firewall on port 143 within ISPConfig is disabled. Within Outlook Express i receive the error code: 800ccc0e This means that a connection is not possible. My conclusion is that i can not establish a connection via port 143 from outsite the mailserver. Any suggestions to solve this problem?