Splitting traffic between IPv4 and IPv6 for the same provider

KumoMTA Configuration
1

Hello ! :slight_smile:

We are currently introducing IPv6 addresses into our existing sending pools, alongside our IPv4 addresses.

For providers that accept inbound email over IPv6, such as Gmail, we don’t necessarily want Kumo to move 100% of the eligible traffic to IPv6.

Our goal would be to keep traffic distributed between both address families. For example:

  • ~2/3 of the traffic sent over IPv6

  • ~1/3 of the traffic kept on IPv4

There are two reasons for this:

  1. We want to maintain regular traffic on our existing IPv4 addresses so their reputation doesn’t become “cold”.

  2. Some of these IPv4 addresses may later be assigned as dedicated IPs to customers, so keeping some traffic flowing through them is useful for maintaining/warming their reputation beforehand.

Ideally, we would like to control this ratio per provider or destination, since IPv6 support obviously varies between receiving networks.

Is there a recommended way in Kumo to implement this kind of weighted IPv4/IPv6 traffic distribution?

For example, can this be achieved through source selection / source pools, or would we need to create separate IPv4 and IPv6 sources/pools and implement the weighting ourselves in Lua?

The important point is that we’re not looking to use IPv6 only as a fallback for IPv4. We want both IPv4 and IPv6 to actively carry traffic, but with a configurable distribution between them.

Thanks! :slight_smile:

2

This could be done in creative ways in Lua, but assuming you’re using the helpers then yes, create a pool with both and do weighting to control the split between IPv4 and IPv6.

3

I’ll pass it on my devs so they try this !

Thanks !