IP Warm-Up Recommendations
Here are our recommendations on warming up IP addresses.
What this document assumes
(Note: These recommendations assume that you are sending wanted and expected email. It is possible that with unwanted or unexpected email that these recommendations may actually hurt your deliverability compared to other strategies.)
For more information on why using these techniques for unwanted or unexpected email, read the article Two Worlds of Email Deliverability.
Why a warm-up is required
When an IP address has not previously sent email it must be “warmed up”. Warming up an IP address means that you gradually increase the volume and build a “credibility” or a “reputation” with ISPs that you send good email from that IP address.
This is required because ISPs are very suspicious of email from that IP address. The fact is that 99 times out of 100, when a new IP address starts sending email, it is a spammer that was blocked on one IP and is moving to another IP. At the time of starting a warm-up, your reputation is not neutral but actually slightly negative.
The ISPs also have throttles that will limit the amount of email accepted from an IP address. Because of this, with a warm-up you must start sending a small amount of email, establish a good reputation at that volume, and then gradually increase the amount of email you send.
What to expect from a deliverability perspective
Unfortunately, you will not get your best deliverability at the beginning of a warm-up. In our experience, about 75% of the time the very first campaign on a new IP address goes to the Spam folder at Gmail.
If your early campaigns are going to the Spam folder, don’t worry – this is normal. If you are sending good email, the ISPs will figure it out.
What to do
Determine the number of IP addresses and IP segmentation strategy
Our recommendations on forming an IP address allocation strategy can be found here:
And our advanced article is here:
Advanced IP Segmentation and Allocation
We recommend putting transactional email on its own IP address separate from marketing email.
If you are using multiple IP addresses, only start sending sending email on three IP addresses at the beginning of the warm-up. Then every three days add in a new IP address. If too many IP addresses start sending mail at the same time this looks very suspicious to the ISPs.
Ramp up volume but start with your best data
We recommend starting sending about 5,000 messages per day from each IP address to each ISP. Typically the largest ISP is about 25% of a typical mailing list, so this works out to sending 20,000 messages per day from each IP address.
This volume can be increased 50% each week, as long as:
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There is no push-back from the ISPs, meaning no high deferral or failure rates.
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You have been regularly sending. For example, if you stop sending for a week, then the time that you were not sending does not count towards your warm-up.
During the warm-up process, as part of your “initial deliverability consulting package,” we will monitor your email volume and will advise on when the volume should be increased.
We recommend that on a new IP you start with email addresses that have recently clicked or opened an email from you. This is a form of putting your “best foot forward.” The ISPs are naturally suspicious of email from new IP addresses (because 99 times out of 100 it is a spammer moving to a new IP address because the old IP was blocked). You want to overcome this suspicion with your best content and your most engaged recipients.
If the number of recent clickers and openers don’t support sending 20,000 messages/day or 5,000 messages/day per ISP on each new IP, then you should reduce the number of IP addresses to keep the per-IP volume good.
Throttle the speed of your sending
We recommend throttling the speed that you inject mail into GreenArrow Engine. When warming up, each day’s sending should take at least four hours for the messages to be delivered into GreenArrow Engine. If possible, throttle down to an eight hour delivery time – although not every business is able to do this.
If you are using GreenArrow Studio, throttle the speed of injection by setting the “speed” setting in a campaign. If you are sending 20,000 messages, then a speed of “5000” will cause the creation of these messages to take four hours.
As the warm-up increases, this speed can be increased.
Use GreenArrow Monitor
Use GreenArrow Monitor for all of your campaigns during the warm-up period. This gives us really valuable data to work with. Don’t worry about using too many GeennArrow Monitor events in the warm-up phase – as part of your “initial deliverability package” there is no charge in the warm-up period.