Dovecot can’t start with error pop3-login & imap-login not supported protocol family

vim /etc/dovecot/dovecot.conf
—
listen = *, ::
?
listen = *
—
service dovecot restart

If you see this error after Dovecot 2.0.x was installed:
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
it means that Dovecot is trying to bind to an IPv6 interface, but your system doesn’t support IPv6.  The solution is to tell Dovecot to only listen on an IPv4 interface.  You can do this by adding the following to the very top of your /etc/dovecot.conf file
listen = *
The internal default is
listen = *, ::