I am having an issue with postfix/courier after a software update in which courier is no longer listening on the IPv4 ports. Here is the netstat output:
ubuntu@ip-10-x-x-x:~$ sudo netstat -plnt
sudo: unable to resolve host ip-10-0-4-32
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:783 0.0.0.0:* LISTEN 1178/perl
tcp 0 0 0.0.0.0:465 0.0.0.0:* LISTEN 3841/master
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1078/sshd
tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 3841/master
tcp 0 0 127.0.0.1:10024 0.0.0.0:* LISTEN 1173/amavisd-new (m
tcp 0 0 127.0.0.1:10025 0.0.0.0:* LISTEN 3841/master
tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN 1127/mysqld
tcp 0 0 0.0.0.0:587 0.0.0.0:* LISTEN 3841/master
tcp6 0 0 :::110 :::* LISTEN 1854/couriertcpd
tcp6 0 0 :::143 :::* LISTEN 4172/couriertcpd
tcp6 0 0 ::1:783 :::* LISTEN 1178/perl
tcp6 0 0 :::22 :::* LISTEN 1078/sshd
tcp6 0 0 :::993 :::* LISTEN 4124/couriertcpd
tcp6 0 0 :::995 :::* LISTEN 1883/couriertcpd
As you can see, ports 110, 143, 993, and 995 only appear to be open on the IPv6 interface. This is causing connectivity problems for several mail clients.
Here are my config files:
In /etc/postfix/main.cf, I have
inet_interfaces = all
inet_protocols = ipv4
In /etc/courier/imapd-ssl.dist, I have:
SSLPORT=0.0.0.0.993
SSLADDRESS=0.0.0.0
In /etc/courier/imapd.dist, I have:
PORT=0.0.0.0.143
ADDRESS=0.0.0.0
And of course I did:
sudo /etc/init.d/courier-imap restart
sudo /etc/init.d/courier-imap-ssl restart
And no luck...
As a temporary fix, I have added a public DNS entry for the IPv6 address of this host, and mail seems to be coming in now.