IPv6 will change how we use the internet, again. To the typical user, there is no difference; web sites work the same. But email is a different story.

When using IPv6, addresses are allocated in a different manner. Most end-users today get one IP address, which is shared between multiple machines using a Network Address Translation (NAT) router. In IPv6, each user gets an address block – a /64 – of address space. This is great news, because end-to-end application on the Internet will work much better, and there will be no NAT in the way.

A /64 is a huge amount of space – 18,446,744,073,709,551,616 IP addresses, to be precise. Looking at it another way, each end-user will get more than all of the address space available on the existing IPv4 internet. 4 billion times more!

That means that each of the devices in your home – your computers, phones, tablet computers, game centers, etc – all have their own address. There is no configuration required for this – it just works.

Unfortunately, this is also going to make it easy for spammers. Today, we can block spam by refusing mail from the IP address it is coming from. With more than 150M computers sending spam, this is hard – but we can do it.

With IPv6, the spammers can change. Because they get a block of addresses, they can send 1,000,000,000 spam messages each second, each using a different IPv6 address, for 500 years before they have to re-use an address! And, when they run out, they can just disconnect their modem, re-connect it, and get a new address block to do it all over again.

We’ve come up with the technology to deal with this, and will be making it available as IPv6 use increases over the coming months.