List Warming Guide


List warming allows you to gradually add volume over time to build a positive reputation with an email service. This feature is recommended if you're starting to mail on a new domain, IP address, switching email marketing service providers, or haven't sent to a list in awhile. List warming is a superset of IP warming, as it can be used to both warm a new IP or a specific sender/content to an active IP address. Whereas IP warming mainly focuses on warming a new or underused IP address.

List warming is not a guaranteed process and is not a one size fits all solution. Warming a list successfully requires time and dedication to complete properly. We recommend reading through our entire list warming guide to best prepare yourself for success.

Preparation Before Warming A List

When choosing a list to warm there are a few things we would recommend doing to ensure the best possible results.


Comb through your list to ensure you're warming up with your most engaged data first. The first couple of weeks are vital, send to people who have engaged or purchased from you in the last 30-60 days, if possible. Slow and steady wins the race in regards to list warming. Aggressive timetables are more volatile and provide little room for adjustment.


When picking the mailing content to send to your list, choose content that has performed favorably in the past with high engagement. Avoid sending content that can be seen as niche unless your list is highly segmented towards that audience. The more you know about the recipients' interests you're sending to the better. Knowledge is power. Sending an offer or newsletter to someone interested in that topic is always more likely to lead to engagement. Check that your content is displaying consistently across all modern devices by running a Litmus Inbox Preview.


Consider running a list cleaning on your data. One of the most harmful things when warming a list is sending to spam traps. Spam traps alert the mailbox provider that you're sending to disengaged recipients. Many times, these spam traps open or click on your messages and can be near impossible to distinguish from legitimate customers. Strict data management can cut down on spam traps, but a list cleaning is always recommended.


Follow data collection best practices and send to contacts who have given their permission to receive mail. Recipients will complain heavily if the mail they're receiving is not expected. Do not send more frequently than initially advertised. Send relevant content to what they signed up for. Do not be misleading with your offers. Opt-in data will always have the best engagement and give you the best chance at the inbox.

How To Build Your Sender Reputation

Sender reputation is what mailbox providers associate you with when you send an email. This is often keyed off of several factors: domain, IP address, and content. That leaves the question, what impacts your sender reputation?

Things that help your sender reputation:

*DKIM, SPF, and DMARC don't directly affect your sender reputation, but they can protect you from bad actors trying to harm your reputation. See the technical records section below.


Things that can hurt your reputation are common pitfalls but can be easily avoided if you're paying attention to your reports and managing your list data properly.

Things that hurt your sender reputation:

  • Spam traps
  • Large spikes in email volume
  • Spam complaints
  • Sending to invalid addresses (hard bounces)
  • IP and Domain Listings
  • Problematic content
    • i.e. dating offers, cryptocurrency, online trading, gambling, etc.

Keeping these in mind when sending gives you the best chance at success. When using a list warming process, you should always anticipate some spam placement and soft bouncing to occur. It is important to keep following best practices and stick to the plan. Email services will adjust as they see consistency and engagement on your list. However, there is a fine line between stats that will turn around and ones that are destined to fail. If you're seeing large quantities of rejections and little traction on your engagement, you may need to pause your list warming and re-evaluate your plan.

Feel free to contact us if you're seeing any results that seem troubling and we would be more than happy to advise you. This feature is available to Pro plans and can be accessed via the user interface. For more instructions on how to use this tool, click here.

Technical Records (DNS)

Technical records, DNS records like SPF, DKIM, and DMARC, help you govern your brand and build trust in your domain. Adding DKIM and SPF records to your sending domains is a best practices as they help you establish trust in your brand/IP/domain. DMARC combines SPF and DKIM, and adds a further layer of trust by requiring DMARC Alignment: when the from-address, return-path, spf, and dkim all use the same domain.

DMARC also provides the option to receive reports about mail from you domain and lets you set how mailbox providers handles your messages when DMARC evaluation fails. Even though it is not required for your emails to reach the inbox, a DMARC policy of p=reject can ensure that unauthorized messages from your domain are easily identifiable by mailbox providers and help you root out abuse that can cause damage to your reputation.

  • SPF - A list of IPs authorized to send email for your domain
  • DKIM - An authoritative, digital signature pair, wherein ReachMail holds a private key, and your DNS record holds a public key. Receiving mail servers are able to verify 
  • DMARC - A policy you set for how mailbox providers should treat messages from your domain with regards to SPF, DK
  • Branded/Custom Tracking Domains - URLs in your email content can be branded with your domain for link tracking.
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