Re: Is there a way to avoid using IPv6 in outgoing SMTP connections?

Hi,

On Fri, Jun 19, 2026 at 04:47:37PM +0200, Fabio Muzzi via Exim-users wrote:
>Hi, I have issues sending email using ipv6 because my VPS provider (OVH) allocates a single ip /128 to each vm, and of course a lot of neighbor addresses (inside the /64) are in blacklist, so I'm in blacklist too. This is a known problem since forever but they just don't fix it. It would require a major overhaul of the v6 allocations for the whole infrastructure.

My first recommendation would be to move your VPS to a provider who has 
properly understood how IPv6 is supposed to work.
My second guess is that your IPv4 addresses might also be on a list of 
blacklists, since OVH doesn't have a very good reputation.
My third recommendation would just to add an iptables rule to reject 
outgoing IPv6 connections to tcp/25. exim is supposed to fall back to 
IPv4 then.

If the solution is disabling IPv6 then things are still broken.

Greetings
Marc

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