IP warming best practices

Jul 12, 2018
Brad Gurley

IP warming is a process where organizations that are starting to mail from fresh IPs and domains gradually ramp up their volumes while ISPs (internet service providers) assess the quality of the new mail stream. The goal is to establish a strong sender reputation by slowly ramping up to full volume, starting with your most engaged subscribers over a period of time. Typically, the IP warming process takes ~3-6 weeks but will vary with each sender.

Why is IP warming necessary?

ISPs look at previous send history from an IP and domain when determining whether to accept, block, or filter a message to their customer’s mailbox. New IPs and domains without any previous history are deemed suspicious to ISPs — “What you have done in the past is a great indication of what you will do tomorrow.” This process helps ISPs distinguish legitimate senders from spammers.

“IP warming can be one of the biggest pains from migrating ESPs”

Back in simpler times, ISPs would primarily look at IP traffic when evaluating a brand’s sending reputation. Over recent years, major ISPs like Gmail and Hotmail have started to weigh domain reputation as heavily, if not more, than IP reputation.

When high-volume enterprise businesses migrate to a new ESP, you will typically receive a set of new dedicated IPs and sending domains. With MessageGears, our deliverability team will ensure your IPs and domains are properly white-labeled, enrolled in all available FBLs (feedback loops), and passing authentication protocols (SPF, DKIM, DMARC) prior to your go-live date. We will also tailor a specific ramp-up plan and guide you through the entire process in order to ensure a successful migration.

As most email marketers know, IP warmup can be one of the biggest pains from migrating ESPs — but with proper guidance and these best practices, it will help make that transition as smooth as possible.

IP warming best practices

When talking about IP warming with any ESP, you will hear a somewhat similar but likely different approach. This doesn’t necessarily mean one is better than the other; it’s just that there are various ways to accomplish a successful warmup — whether it’s broken down by domain, in daily volume increments, or weekly volume increments. There isn’t one cookie-cutter formula for warmup — it will vary with each sender as volume, cadence, content, IP allocation, user engagement, and data hygiene all differ from brand to brand.

Even when you do everything ‘right,’ you may still run into some temporary blocks or spam filtering initially as ISPs adjust to the new mail stream. Ultimately, their goal is always to protect their consumers from spam and only deliver wanted mail.

While the plans themselves may differ, they should all follow these best practices:

Warm up your IP/domain using your best-performing campaign


    1. Use a campaign with high user engagement and low complaints/unsubscribes.
    2. Use a non time-sensitive campaign, so that volumes and cadence are more flexible.

Start slowly with your most engaged subscribers


    1. In order to establish a strong sender reputation, always start with your most engaged subscribers while gradually increasing volume (i.e. start with users that have opened/clicked a message in the past 30 days, then open up to 60-day actives and so on, until you’ve reached full volume)
    2. Using your most engaged audience will also help eliminate risk of high complaints, hard bounces, and trap hits — all factors that are detrimental to sender reputation, especially during warmup.

Monitor performance closely and adjust as appropriate


    1. It’s important to make adjustments to your warmup plan as appropriate — for example, if ISPs are seeing very positive metrics (opens, clicks) they may allow you to send higher volumes than what was initially recommended by your ESP. Contrarily, if ISPs are seeing negative metrics (complaints, unsubscribes, hard bounces, spam traps) and begin throttling your traffic, it may be time to slow things down.
    2. With MessageGears, you will have a dedicated deliverability specialist monitoring each send, addressing any potential issues, and making adjustments as necessary throughout the process.
    3. Most deliverability issues occur during the IP/domain warmup period — using third-party inbox and reputation-monitoring tools like 250OK is a great way to help monitor sends, especially during warmup.

While there’s plenty more to address with IP/domain warmup, these best practices will help put you on the right path for a smooth and successful IP warming. For more information on optimizing your email marketing efforts and getting to the inbox, check out Five Best Practices for Email Deliverability.

About the Author

Brad Gurley

Serving as MessageGears’ Director of Deliverability, Brad spends his days watching mail queues, analyzing customer delivery data, and researching the latest updates to email technology. He’s been in the email marketing space for the better part of two decades and harbors a passion for educating senders on how to more effectively deliver mail to their subscribers. When he’s not busy updating MTA configurations, you might find him preparing a variety of smoked meats or leading a group of friends to the closest karaoke bar.