报错信息：
[root@VM_0_4_centos ~]# service dovecot start
Starting Dovecot Imap: Error: socket() failed: Address family not supported by protocol
Error: service(pop3-login): listen(::, 110) failed: Address family not supported by protocol
Error: socket() failed: Address family not supported by protocol
Error: service(pop3-login): listen(::, 995) failed: Address family not supported by protocol
Error: socket() failed: Address family not supported by protocol
Error: service(imap-login): listen(::, 143) failed: Address family not supported by protocol
Error: socket() failed: Address family not supported by protocol
Error: service(imap-login): listen(::, 993) failed: Address family not supported by protocol
Fatal: Failed to start listeners
[FAILED]
原因：不支持ipv6（其中的一种可能性）
解决办法：修改dovecot.conf
# vi /etc/dovecot/dovecot.conf第26行改为
listen = *重新启动
[root@VM_0_4_centos ~]# service dovecot start
Starting Dovecot Imap: [ OK ]
