[Users] Disable IPv6

[Slavko]

Dňa 16. júla 2022 16:44:08 UTC používateľ Edward <epp at caramail.com> napísal:
>On 7/16/22 10:51, Marco wrote:
>> Am Sat, 16 Jul 2022 07:20:31 -0400
>> schrieb Edward <epp at caramail.com>:
>> 
>>> I am familiar with A and AAAA records. The IMAP server is running
>>> Dovecot and DNS is showing it has has 16 IPv4 addresses. Apart from an
>>> online support forum, there is no direct way to contact the server
>>> admins.
>> Does it also have AAAA records?
>> Why don't you tell us the domain name, we might check it.
>
>Yes, it also has AAAA records: imap.comcast.net

connection to it via both IPv6 and IPv4 works (i tried plain only,
but 993 is open too), they do not force IPv6 as you stated in first
message,

Thus we need go back to your machine. Nowadays OSs works
without problems in both, mixed IPv4/IPv6 and IPv4 only environments.
If you are not using somthing very old (or strange), there must be
no problem if DNS returns both A/AAAA record and OS will select
proper IP family. In your case it must select IPv4, if outgoing interface
has no global (ULA  are global too) address(es) without touching
previously mentioned gai.conf nor addrlabel. To be sure that you have
not global IPv6 address configured, check your interfaces configuration.

You mention that you have to disable IPv6 in Thurderbird, that points,
that you have something wrong in your network configuration. I use it
in IPv4 only environment (even with old Win7) and i have no problems...

You mentioned virtual machine, buf didn't tell about its virtual
network. Virtualization can do strange things with network, which
can be not visible at first look. You have to inspect/understand
particular virtual networking properly, and of course, check your
firewall...

́Disabling IPv6 in nowadays is something, what must be not needed.
It was usefull 10 (or more) years ago. By the google's stats, near
50 % of the world is using IPv6, and that number is growing (except
our country -- he he)... AFAIK, there is even growing number of hosts
using IPv6 only...

The only group staying on IPv4 seems to be spammers yet ;-) (beside
gmail no one attempt to deliver SPAM via IPv6 to my servers).

regards
Slavko