Re: IPv6 recap

Sam Varshavchik <[email protected]> Fri, 05 Apr 2024 18:41:50 -0400
Newsgroups	gmane.mail.imap.courier.general
Message-ID	<[email protected]>
Joe Laffey writes:

> On Fri, 5 Apr 2024, Joe Laffey wrote:
>
>> On Fri, 5 Apr 2024, Sam Varshavchik wrote:
>>
>>> Joe Laffey writes:
>>>
>>>>
>>>> After I disabled IPV6 it still didn't work. Courier tries to bind to a non- 
>>>> existent IPv6 address (none is assigned at all, IPv6 disabled, and no IPv6  
>>>> shows up in 'ip a' output).
>>>
>>> Check for the ipout configuration file, which explicitly sets outbound IP  
>>> addresses.
>>
>> Thanks for this; however, I had this set as well.
>>
>> My ipout has only one line, the ipv4 address.
>>
>> So with IPv6 disabled in both sysctl and in the bootloader, and no ipv6  
>> address assinged in netplan (nothing in 'ip a'), and ipout set to a single  
>> line of the ipv4 address I still get "Cannot Assign requested addreess" when  
>> an address has an ipv6 MX.
>>
>
>
> Replying to myself. I had no ip6out file at all, only an ipout with the  
> single ipv4 address in it.
>
> Would I need to have and ip6out that is blank to avoid courier trying to use  
> ipv6 like I describe above?

No, that should not be necessary.

Double-check that the ipv4 address, for this MX, is actually reachable.

If there are multiple IP addresses, either IPv4 or IPv6, each one is tried.  
If a connection to one of them fails for any reason the next one should be  
tried. After the connection to an IPv6 address fails Courier should then try  
the IPv4 address.

Now, if both of the IP addresses are unreachable, and the IPv4 address was  
tried first, the logged error would be the error that was logged from the  
last connection attempt, and if it was the IPv6 one then you'll just see  
that error.

I think that's what's happening in your case.

I have no issues sending mail to gmail.

[mrsam@jack rfc1035]$ testmxlookup gmail.com
Domain gmail.com:
STS: enforcing
Relay: gmail-smtp-in.l.google.com, Priority: 5, Address: ::ffff:142.251.167.27
Relay: gmail-smtp-in.l.google.com, Priority: 5, Address: 2607:f8b0:4004:c1d::1a
Relay: alt1.gmail-smtp-in.l.google.com, Priority: 10, Address: ::ffff:209.85.202.27
Relay: alt1.gmail-smtp-in.l.google.com, Priority: 10, Address: 2a00:1450:400b:c00::1a
Relay: alt2.gmail-smtp-in.l.google.com, Priority: 20, Address: ::ffff:64.233.184.27
Relay: alt2.gmail-smtp-in.l.google.com, Priority: 20, Address: 2a00:1450:400c:c0b::1b
Relay: alt3.gmail-smtp-in.l.google.com, Priority: 30, Address: ::ffff:142.250.27.26
Relay: alt3.gmail-smtp-in.l.google.com, Priority: 30, Address: 2a00:1450:4025:401::1a
Relay: alt4.gmail-smtp-in.l.google.com, Priority: 40, Address: ::ffff:142.250.153.27
Relay: alt4.gmail-smtp-in.l.google.com, Priority: 40, Address: 2a00:1450:4013:c1

I have only IPv4 addresses.

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