Cannot disable IPv6 components on exchange server without breaking exchange

Question

I've got an issue with an exchange 2013 server. Any mail being sent to a gmail recipient is rejected due to IPv6 issues, with the following bounceback...

mx.google.com gave this error: [2002:c30a:e196::c30a:e196] Our system has detected that this message does not meet IPv6 sending guidelines regarding PTR records and authentication. Please review https://support.google.com/mail/?p=IPv6AuthError for more information . j10si13286393wrc.204 - gsmtp Your message wasn't delivered due to a permission or security issue. It may have been rejected by a moderator, the address may only accept email from certain senders, or another restriction may be preventing delivery.

The machine doesn't use IPv6 at all, so I opted to add a entry to the registry in the following location, as suggested here...

hkey_local_machine\system\currentcontroset\services\tcpip6\parameters\

I added a Reg_dword titled disabledcomponents with a decimal value of 255 and rebooted the system.

When it came back online, most of the exchange services were stuck in 'starting'.

I removed the reg entry in question and rebooted, and we're back to normal, however I still have the mail delivery issue.

Has anyone come across this before? pretty much all of the results I can find with this end with this reg key being added and the issue being resolved.

Any help appriciated.

My IPv6 Preference list looks like this...

 Precedence  Label  Prefix
 ----------  -----  --------------------------------
    50      0  ::1/128
    40      1  ::/0
    35      4  ::ffff:0:0/96
    30      2  2002::/16
     5      5  2001::/32
     3     13  fc00::/7
     1     11  fec0::/10
     1     12  3ffe::/16
     1      3  ::/96

Solution

That is a legacy 6to4 address, a deprecated IPv6 transition technology. To solve the problem, you need to disable 6to4 on your server.

From PowerShell as Administrator:

Set-Net6to4Configuration –State disabled

While you're at it, you should also disable other IPv6 transition technologies that are known to cause problems, Teredo and ISATAP:

Set-NetTeredoConfiguration –Type disabled
Set-NetIsatapConfiguration –State disabled

Comments

[John]

ok, which ones for my list? Precedence Label Prefix ---------- ----- -------------------------------- 50 0 ::1/128 40 1 ::/0 35 4 ::ffff:0:0/96 30 2 2002::/16 5 5 2001::/32 3 13 fc00::/7 1 11 fec0::/10 1 12 3ffe::/16 1 3 ::/96

[Brian]

Your list already has IPv4 preferred. Your Exchange server is unlikely to be what is making the IPv6 connections to external mail servers. Outbound mail is likely being put through a proxy or gateway at your firewall which is sending them on over IPv6.

[John]

It definately isn't in this case... Its a standalone exchange server with no proxy. :(

[Ron Maupin]

The host also seems to be using the deprecated Site-Local address in the precedence list: fec0::/10.