[Users] Issue with ipv6 mail checking timing out

[Chris Schrauben]

On Thu, 23 Jul 2020 07:28:08 -0400
Jerry <jerry at seibercom.net> wrote:

> On Thu, 23 Jul 2020 18:16:11 +0800, Chris Schrauben stated:
> >The last two days I have been unable to fetch mail (timed out) from
> >my Gmail (1) and Outlook (4) accounts. At first I was thinking my ISP
> >(their service is not so good). I did some troubleshooting. These are
> >POP3 accounts. I will use Gmail as the example, results are the same
> >with Outlook using both pop-mail.outlook.com and
> >outlook.office365.com.
> >
> >'telnet pop.gmail.com 995, result with "Trying
> >xxxx:xxxx:xxxx:xxx::xx...trying to connect"
> >
> >Using ping -4 pop.gmail.com to get the ipv4 address I try 'telnet
> >xxx.xxx.xxx.xxx 995 and get "Trying xxx.xxx.xxx.xxx... Connected to
> >xxx.xxx.xxx.xxx."
> >
> >I don't see a way to force ipv4 by account, I do know there is a
> >--disable-ipv6 configure option. So I rebuilt claw-mail with that
> >option. All is well... for now. 
> >
> >Has anyone else experienced this issue (works with -ipv4, not with
> >-ipv6).
> >
> >Before this I was having constant timeout problems with Gmail,
> >sometimes it works some times it doesn't. I am now thinking this may
> >have been the reason, when it worked an -ipv4 address was used, when
> >it didn't it was -ipv6. 
> >
> >Thanks, Chris
> 
> https://support.google.com/mail/answer/7104828?hl=en
> 
> You need SSL for POP3. Telnet does not supply that. Use:
> 
> openssl s_client -connect pop.gmail.com:995 -showcerts
> 
> Post the results.
> 
Let me try again to communicate my issue. 

I have several POP3 accounts. They all work perfectly except for 5 of
them. One is a Gmail account. The other four are Outlook accounts. 

I used telnet only to verify a connection. As you can see in my initial
post telnet does not connect using an ipv6 address. Telnet does connect
using an ipv4 address.

That led me to trying to find a way to force claws-mail to use ipv4
addresses. There is no way I could find except rebuild claws-mail with
"--disable-ipv6". After doing so those account now work just fine.

I was asking if anyone else has had this problem. That problem being
works with ipv4, not working with ipv6. 

Entering the command above, I get:
openssl s_client -connect pop.gmail.com:995 -showcerts
Sits there doing nothing until I use Ctrl-C

If I use that command above with an ipv4 address (resolved using
'ping -4 pop.gmail.com) I get the following (first few lines):

openssl s_client -connect 74.125.24.108:995 -showcerts
CONNECTED(00000003)
Can't use SSL_get_servername
depth=0 OU = "No SNI provided; please fix your client.", CN =
invalid2.invalid verify error:num=18:self signed certificate
verify return:1

The output of gnutls-cli pop.gmail.com:995 is as follows:

gnutls-cli pop.gmail.com:995
Processed 134 CA certificate(s).
Resolving 'pop.gmail.com:995'...
Connecting to '2404:6800:4003:c00::6d:995'...
I used Ctrl-C to get out.

The output of gnutls 74.125.24.108:995 is as follows (First few lines):

chris at racermach:~$ gnutls-cli 74.125.24.108:995
Processed 134 CA certificate(s).
Resolving '74.125.24.108:995'...
Connecting to '74.125.24.108:995'...
- Certificate type: X.509
- Got a certificate list of 1 certificates.