Why do we "warmup" IP addresses

IP address warmup is a big issue for anyone moving to a new IP address for sending.
I’m constantly being asked how to warm up an IP. My answer is always the same. There’s no right way to warm up an IP nor is there a specific formula that everyone should follow.
What warming up is about is introducing mail traffic to receiving spam filters in a way that lets the filter know this is a legitimate email stream. This means sending small but regular amounts of mail that recipients interact with. As the filters adjust to the amount of mail from that IP, more mail can be sent over that IP. Increase the mail volume over the next few weeks until the desired volume is reached.
There are a couple things to remember about warming up.

  • Warming up is about the regular volume from an IP. IPs cannot be “pre warmed” and then left without traffic. Stop mailing from that IP and lose any benefit gained.
  • Warming an IP will not compensate for poor practices. You can only warm an IP to the reputation of the mail sent from that IP.
  • Warming creates a reputation, but that reputation is not permanent. Changing mail sent over the IP can increase or decrease the reputation of the IP.

So what’s the best way to warm up an IP? There really isn’t a best way. Each IP warms differently. There are some guidelines, however,

  • Send first to your best, most active customers.
  • Send consistently.
  • Start with a hundred or so messages an hour.
  • Increase the hourly rate gradually.
  • Monitor your logs.
  • If the ISPs start sending back 4xx failures, you’re going too fast so slow down.
  • Don’t try to start a new IP and a brand new domain at the same time.

 

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Hunting the Human Representative

Yesterday’s post was inspired by a number of questions I’ve fielded recently from people in the email industry. Some were clients, some were colleagues on mailing lists, but in most cases they’d found a delivery issue that they couldn’t solve and were looking for the elusive Human Representative of an ISP.
There was a time when having a contact inside an ISP was almost required to have good delivery. ISPs didn’t have very transparent systems and SMTP rejection messages weren’t very helpful to a sender. Only a very few ISPs even had postmaster pages, and the information there wasn’t always helpful.
More recently that’s changed. It’s no longer required to have a good relationship at the ISPs to get inbox delivery. I can point to a number of reasons this is the case.
ISPs have figured out that providing postmaster pages and more information in rejection messages lowers the cost of dealing with senders. As the economy has struggled ISPs have had to cut back on staff, much like every other business out there. Supporting senders turned into a money and personnel sink that they just couldn’t afford any longer.
Another big issue is the improvement in filters and processing power. Filters that relied on IP addresses and IP reputation did so for mostly technical reasons. IP addresses are the one thing that spammers couldn’t forge (mostly) and checking them could be done quickly so as not to bottleneck mail delivery. But modern fast processors allow more complex information analysis in short periods of time. Not only does this mean more granular filters, but filters can also be more dynamic. Filters block mail, but also self resolve in some set period of time. People don’t need to babysit the filters because if sender behaviour improves, then the filters automatically notice and fall off.
Then we have authentication and the protocols now being layered on top of that. This is a technology that is benefiting everyone, but has been strongly influenced by the ISPs and employees of the ISPs. This permits ISPs to filter on more than just IP reputation, but to include specific domain reputations as well.
Another factor in the removal of the human is that there are a lot of dishonest people out there. Some of those dishonest people send mail. Some of them even found contacts inside the ISPs. Yes, there are some bad people who lied and cheated their way into filtering exceptions. These people were bad enough and caused enough problems for the ISPs and the ISP employees who were lied to that systems started to have fewer and fewer places a human could override the automatic decisions.
All of this contributes to the fact that the Human Representative is becoming a more and more elusive target. In a way that’s good, though; it levels the playing field and doesn’t give con artists and scammers better access to the inbox than honest people. It means that smaller senders have a chance to get mail to the inbox, and it means that fewer people have to make judgement calls about the filters and what mail is worthy or not. All mail is subject to the same conditions.
The Human Representative is endangered. And I think this is a good thing for email.

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IP Address reputation primer

There has been a lot of recent discussion and questions about reputation, content and delivery. I started to answer some of them, and then realized there weren’t any basic reference documents I could refer to when explaining the interaction. So I decided to write some.
This first post is about IP address reputation with some background on why IPs are so important and why ISPs focus so heavily on the sending IP.

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Yes, we have no IP addresses, we have no addresses today

We’ve just about run out of the Internet equivalent of a natural resource – IP addresses.

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