Not having IPv6 connectivity isn’t really a reason for having to deactivate it on your machines. Sure, network adapters will have a link-local address set (fe80:…
), but that doesn’t interfere with local networking or internet access. Dual-stack hosts will only chose to connect via IPv6 if they have a globally-routable unicast address. Having link-local addresses doesn’t suffice.
Having a server such as Dovecot listening on IPv6 is actually even less of a problem. Note that the following output actually means that the service listens on both IPv6 and IPv4, not just on IPv6:
[0 root@liselle ~] lsof -PniTCP:8090 -sTCP:LISTEN
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
java 220 mailarchiva 50u IPv6 82207 0t0 TCP *:8090 (LISTEN)
[0 root@liselle ~] telnet -6 localhost 8090
Trying ::1...
Connected to localhost.
Escape character is '^]'.
^]
telnet> quit
Connection closed.
[0 root@liselle ~] telnet -4 localhost 8090
Trying 127.0.0.1...
Connected to localhost.localdomain.
Escape character is '^]'.
^]
telnet> quit
Connection closed.
[0 root@liselle ~]
What are your actual problems with IPv6?