启动dovecot报错Address family not supported by protocol

正在启动 Dovecot Imap：Error: socket() failed: Address family not supported by protocol
Error: service(managesieve-login): listen([::], 4190) failed: Address family not supported by protocol
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(lmtp): listen([::], 24) 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

这是因为系统不存在ipv6, 解决办法:
vi  /etc/dovecot/dovecot.conf  
把listen = * [::]改为listen = *