Hi everyone, I have our mailcow server setup and running and everything is going ok, except that our IP6 IP range (not our actual address, the whole block!) is listed on Spamhaus so our customers get bounce backs if the recipient mail server does spamhaus lookups. Our IP4 address is not listed though. Would you advise that we turn off sending outgoing emails from our IP6 address, or will/could that cause other issues down the line?

I would suggest to make sure you are not sending spam and than request de-listing. Make world a better place,...

We are definitely not sending spam and have requested a delisting. I think the issue is that spamhaus has blocked the whole IP6 "block" that I am on, so it could be another user/server on the same hosting has got themselves blocked, but it is affecting everyone on this ipv6 block

Well based on IP your provider is OVH, according to their help page they are allocating /64 block I would suggest to contact your provider to validate this information. Even RFC state that providet should allocate at least /64 block,... That said previous and next block are not listed, so if first is true than de-list make sure you are not sending spam and you will be good. It may be mess from previous tenant.

Advice for Spanhaus issues

bpsintl

Thanks.

I have an open support ticket with OVH. What can they do though? Is it up to OVH to fix or Spamhaus?

ETNyx

OVH is not responsible for the Spamhaus listing. Just make sure you have /64 block whit OVH and ask for de-listing on Spamhaus, it should be ok

bpsintl

Thank you

bpsintl

I’ve been doing some testing on this. When I send email from my Mail app on my mac, the email is sent via our IP6 address. However, when I login to the mailcow webmail, emails sent out go via our IP4 address and hence are not blocked by Spamhaus checks.

Is this normal?

ETNyx

Seems to be unlikely, that if you submit message over v4 than sending will always be over v4 and vice versa,…

bpsintl

ETNyx sorry, I don’t understand what you mean.

ETNyx

Sorry I have added a layer on top,..

You are conflating message reception and message delivery. These are two separate “daemons”. And I doubt there is a causal relationship between them.

Simply put, you are saying that if your Postfix receives a message using SoGo, it will always use v4 to send it. And if you use Mac app, than v6 to send it. I am saying that this is a correlation, not a causal relationship.

bpsintl

Basically, I logged into sogo and sent an email to an account that I manage (Google account), and sent the same email address another message via my Apple Mac Mail app.

Then in google I opened each email, and “show original”. In the email sent via sogo, the header at the top says SPF PASS then lists my Ip4 address.

When I go the same to the message received from my mac, it says SPF PASS then lists my IP6 address.

My question is why are they different? Why is one sending using IP4 and one IP6?

ETNyx

Sorry I do not have answer for you. Random? Luck? My first thought is that sending to Google is not good for testing. I guess Google use many (a lot of) servers and you are not able to enforce specific server/route to make some kind reliable test.

I was curious and try your test on my instance, when I send from SoGo and Linux/Thunderbird. For me both are delivered to Gmail using IPv6.

bpsintl

Ah ok, thanks. To get around the spamhaus IP6 issue, I have added the following to my /data/conf/postfix/extra.cf

smtp_address_preference = ipv4
smtp_bind_address = [your_ipv4_to_use_for_sending]

Can you see any issues with me doing that? I tested an email from my mac again and it now sends via IP4 not IP6 so it seems to have worked

ETNyx

99.9% Ok,

There can be only v6 servers, sometimes. I got some,.. Even then usually there are v4 backups, or at lest Postifx will delivery MailerDaemon message that this message cant be delivered,..

But I would suggest to re anable v6 after de listing

bpsintl

ETNyx Great, thanks