Summary
Warming up an IP address or subdomain is a critical practice for establishing and maintaining a positive sender reputation, which directly impacts email deliverability. This process involves gradually increasing the volume and frequency of emails sent from a new or previously unused IP or sending domain. By slowly building up your sending volume, you signal to Internet Service Providers (ISPs) that you are a legitimate sender, not a spammer.
Key findings
- Frequency and volume: Warm-up plans must account for both the volume and frequency of your email sends, not just the total number of emails.
- Purpose of warm-up: Warming is primarily for moving an existing mail stream to a new infrastructure (IP, subdomain, DKIM key), rather than for natural organic list growth.
- Subdomain and IP reputation: Even with a warmed IP, a new subdomain still requires attention as reputation is built on a combination of IP, DKIM, and domain name.
- Gradual increase: A gradual increase in sending volume helps ISPs monitor and trust your sending patterns, improving your sender reputation.
- Pre-existing health: The existing mail stream should be healthy (high engagement, low complaints) for at least 1-2 months before any infrastructure changes are introduced.
Key considerations
- Warm-up duration: For weekly sends, the warm-up period will naturally be longer than for daily sends because the total volume is spread out. For more details on this, see how long to warm up an IP address.
- Dedicated IP necessity: If you only send once a week, a dedicated IP might not be necessary, as shared IPs can handle lower volumes efficiently while benefiting from the collective reputation of other senders.
- New mail streams: New newsletter sign-ups or naturally growing lists do not require an artificial warm-up. They will establish their reputation organically over time. This is part of the overall best IP warm-up strategy.
- Combined changes: If you are changing your IP, DKIM, and domain combinations, a structured warm-up or cut-over is the most prudent approach. This is highlighted in Twilio's guide to IP warm-up for email deliverability.
What email marketers say
Email marketers often navigate the complexities of IP and subdomain warm-up based on their specific sending scenarios. They frequently inquire about adjusting warm-up plans for different sending frequencies, such as weekly newsletters versus daily campaigns, and the implications for the time it takes to establish reputation. There is also a common concern about whether a new subdomain needs warming if it's already on a warmed IP provided by an Email Service Provider (ESP).
Key opinions
- Warm-up adjustment: Marketers frequently ask if warm-up plans need to be adjusted for emails sent only once a week, acknowledging it would likely extend the warm-up period.
- Subdomain for future volume: Many marketers look to use subdomains to separate mail streams, particularly when anticipating a future increase in email volume from a specific segment.
- Subdomain warm-up with warmed IP: A common question is whether a new subdomain requires a warm-up even if the ESP is providing an already warmed IP address.
- Established list migration: Marketers recognize that moving an established list to a new subdomain, potentially with a new DKIM key, likely necessitates a proper warming process to maintain deliverability.
Key considerations
- Separate sending streams: Subdomains are often used to separate email types, such as marketing or transactional, which can impact how you warm up a subdomain for email sending.
- Volume and reputation impact: Even if your current volume is low, anticipating a pickup in volume means considering a future-proof warm-up strategy to build a solid email domain reputation.
- Migration planning: When moving an established mail stream, careful planning is essential. As suggested on Mailbluster's guide on warming subdomains, starting with low volumes and gradually increasing is key.
Marketer view
Email marketer from Email Geeks asks about adjusting warm-up plans for emails that are only sent once a week. They wonder if the warm-up process would simply take longer compared to daily sending schedules, given the reduced frequency.
Marketer view
Email marketer from Quora suggests that for new email domains, warming up involves slowly increasing the sending volume to reach normal levels. The duration of this process largely depends on the total number of contacts in the mailing list.
What the experts say
Email deliverability experts highlight that the core purpose of an IP warm-up is to familiarize Mailbox Providers (MBPs) with a new IP's expected email volume and frequency. They emphasize that warm-up strategies primarily apply when migrating existing email streams, not for organic list growth. Experts also point out that sender reputation is a complex combination of IP, DKIM, and domain name, making a structured warm-up prudent when any of these elements change. Maintaining a healthy mail stream before any changes is also crucial to avoid appearing suspicious to receivers.
Key opinions
- Volume and frequency: Experts state that a warm-up plan's main goal is to habituate mailbox providers to both the volume and frequency of email from a new IP.
- Warm-up for migration: Warm-up plans are specifically designed for migrating an existing mail stream to new infrastructure, not for new, organically growing email lists.
- Reputation components: Sender reputation is built around the combination of IP, DKIM, and domain name, making changes to any of these require careful warm-up.
- Healthy mail stream: Before any changes, the existing mail stream should demonstrate high engagement and low complaints for several months to ensure a smooth transition.
- Gradual build-up: Gradually increasing volume builds trust with ISPs and is crucial for high email deliverability, preventing emails from being flagged as spam.
Key considerations
- Dedicated IP suitability: While a warm-up is still needed for weekly sends, a dedicated IP might not be justified if it's the sole purpose, due to its cost and management.
- Shared IP nuance: If moving high volume to a new subdomain on a previously unused shared IP with a new DKIM key, a cautious, case-specific warm-up approach is recommended. This contributes to avoiding why your emails fail.
- Strategic cut-over: A structured cut-over and warm-up process is prudent when changing multiple sending components simultaneously, ensuring smooth transition and reputation transfer. This is part of the best approach for warming up an IP.
- Avoiding suspicion: Introducing changes to an unhealthy mail stream can make a sender appear suspect to receivers, leading to deliverability issues and potential blocklisting (or blacklisting).
- Consistency: Consistent sending patterns are essential for reputation building, as highlighted by experts from SpamResource regarding reputation.
Expert view
Email expert from Email Geeks explains that the core purpose of a warm-up plan is to get mailbox providers accustomed to both the expected volume and frequency of emails originating from a new IP address. This helps build trust with receiving servers.
Expert view
Deliverability expert from Twilio defines IP warm-up as the process of gradually establishing a positive sender reputation for a new or underused IP address. This is achieved by incrementally increasing the volume of email sent over time.
What the documentation says
Official documentation and industry best practices consistently define IP and domain warm-up as the controlled, gradual increase of email sending volume to establish a positive sender reputation. This process is essential for new or inactive sending infrastructures. Documentation emphasizes the importance of a phased approach, starting with low volumes and progressively increasing them, while also monitoring recipient engagement and feedback. Adherence to these guidelines helps prevent common deliverability pitfalls and ensures optimal inbox placement.
Key findings
- Establishing reputation: IP warm-up is defined as establishing a positive sender reputation for new or underused IP addresses.
- Gradual volume increase: The core of warming is incrementally increasing the volume of email sent to allow ISPs to monitor and trust the sender.
- Best practices focus: Documentation provides specific tips and best practices for IP warm-up to improve deliverability.
- Avoidance of spam filters: Proper warming is crucial for avoiding spam filters and ensuring emails reach the inbox effectively.
- Unavoidable process: IP warming is often described as an unavoidable and critical step for new sending infrastructures.
Key considerations
- Phased approach: Documentation often advises a phased approach, starting with very low volumes. For instance, EmailLabs recommends gradually shifting traffic, beginning with a small percentage.
- Monitoring is key: Continuously monitoring engagement, bounce rates, and complaint rates during the warm-up period is essential to adjust sending volumes and content as needed.
- Domain vs. IP warm-up: While often discussed together, it's important to understand the nuances of warming up a domain versus an IP address. Onesignal's documentation on domain vs. IP warm-up provides valuable insights.
- Consistency: Maintaining consistent sending patterns after the initial warm-up period is vital for long-term reputation and avoiding blacklists (or blocklists).
Technical article
Onesignal documentation explains that in situations where IP warm-up is necessary, the process fundamentally involves warming up the associated domain, which in turn establishes the reputation of the IPs used. This integrated approach ensures comprehensive reputation building.
Technical article
Mailgun documentation states that an IP warm-up actively improves your sender reputation by commencing with a small volume of email and then steadily increasing your output. This method enables ISPs to closely monitor your sending behavior.
Related resources
10 resources
Related pages
What is the best approach for warming up an IP address for email sending?
What is the best IP warmup strategy for email sending?
How do you warm up a subdomain for email sending?
How long does it take to warm up an IP address for email marketing?
When switching to a new subdomain for email, what warm-up process is required?
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