How do I warm up a new subdomain for low volume B2B email sends?

Key findings

• Domain vs. IP warming: The primary concern for a new subdomain, especially when using a shared IP from an Email Service Provider (ESP), is domain warming. IP warming is relevant if you have a dedicated IP address, which is typically not recommended for very low sending volumes (e.g., under 50,000 emails per send).
• Reputation inheritance: While subdomains are largely treated separately, a new subdomain can benefit from the positive reputation of its primary domain, making the initial warm-up slightly less stringent compared to a completely new top-level domain.
• Low volume flexibility: For very small senders (e.g., a few thousand contacts) with infrequent sends, the rules for warming up can be more flexible. Traditional warm-up schedules designed for high-volume senders may not apply or could even be detrimental by spreading out sends too thinly.
• Engagement focus: The most effective warm-up strategy involves sending emails initially to your most engaged and active contacts. This helps establish a positive interaction history with mailbox providers early on.
• B2B specific considerations: While B2B has some unique aspects, the core principles of deliverability, including permission and avoiding spam, still apply. Excessive cold email volume can still negatively impact your subdomain’s reputation.
• Spreading sends: Even for low volumes, spreading your initial sends to engaged segments over a few days (e.g., 2-3 days instead of weeks) can be beneficial.

Key considerations

• Define goals: Understand if your primary goal is to separate marketing from transactional emails or to address existing deliverability issues. This will inform your warm-up approach.
• List segmentation: Carefully segment your audience based on engagement levels (active, lapsing, lapsed). Prioritize your most active contacts for initial sends to generate positive engagement signals.
• Monitor engagement: Pay close attention to metrics like open rates, click-through rates, and complaint rates during the warm-up period. High engagement is a strong positive signal. For tools that help with this, consider looking into Google Postmaster Tools.
• Volume increment: Even for low volumes, gradually increasing your sending volume is important. A common starting point for new sending domains is 1,000 to 5,000 emails per day initially, even if your total list is small. You can then quickly ramp up over a few days rather than weeks for a small B2B list.
• Cold email proportion: If you send cold emails, ensure they constitute a very small percentage (ideally less than 10%) of your total sending volume from the new subdomain to avoid damaging its reputation. For more details on this, see warming up a new domain for cold contacts.

Key opinions

• Subdomain separation: Marketers frequently recommend separating marketing communications to a dedicated subdomain to protect the main domain's reputation, especially when migrating data or platforms.
• Domain warming necessity: There's a strong consensus that new subdomains require a warming process because they are treated as distinct entities by ISPs, regardless of the main domain's existing standing.
• Engagement-first approach: Many advocate for beginning the warm-up with the most active and engaged contacts to send positive signals and establish a good sending history. This aligns with overall email deliverability best practices.
• Shortened warm-up for small lists: For databases under 5,000 contacts, especially with low sending frequency (e.g., two emails per month), the warm-up period can be significantly shorter, potentially just a few days instead of several weeks.
• B2B specific flexibility: While B2B emailing allows for some leeway in terms of legitimate interest and cold sending, marketers understand that core spam principles still apply, and reputation must be managed.

Key considerations

• Volume segmentation: Divide your sending list into segments (e.g., active, lapsing, lapsed) and introduce them gradually over a few days rather than sending to the entire list at once. This mirrors general advice on how to warm up a subdomain.
• Sending frequency: Even with low monthly volume, try to spread out your sends within the warm-up period to provide consistent sending signals to ISPs.
• List quality: Before starting, ensure your list is clean and contains legitimate, engaged contacts to minimize bounces and complaints, which are detrimental to a new subdomain's reputation.
• Differentiation of send types: Maintain separate subdomains or sending practices for marketing, transactional, and cold email to prevent one type of sending from negatively impacting the deliverability of others.
• Understand ESP mechanics: Be clear on whether your ESP (e.g., HubSpot) assigns dedicated or shared IPs, as this fundamentally changes your warming strategy (dedicated IPs require rigorous IP warming; shared IPs mean your focus is domain reputation).

Key opinions

• Low volume challenges: Experts note that very low sending volumes and infrequent sends (e.g., two emails per month to 5,000 contacts) might make it difficult for an IP to ever truly become warm, particularly if on a dedicated IP. This reinforces the idea that dedicated IPs are unsuitable for such low volumes, as explained in warming a dedicated IP.
• Domain warming focus: If using shared IPs, the warm-up primarily concerns the subdomain's domain reputation, which is distinct from IP reputation. Subdomains need warming due to starting with no reputation.
• Rapid warm-up for small senders: For very small sender volumes, traditional multi-week warm-up plans are often unnecessary and can be condensed to a few days. The key is consistent, engaged sending within a short period.
• Cold email impact: Even in B2B, sending too much cold email (e.g., over 10% of total volume) can severely harm your domain reputation. Cold emails are still considered spam by ISPs, regardless of perceived B2B leeway.
• IP definition: Experts clarify that an IP address is the numeric identifier for the sending server, emphasizing the difference between warming this and warming a domain.

Key considerations

• Dedicated IP threshold: For dedicated IPs, a minimum send volume of 50,000 emails, sent at least three days a week, is generally recommended to maintain a warm reputation. Below this, a dedicated IP might struggle to stay warm, making shared IPs a better option for low volume. This is discussed in more detail in the best IP warmup strategy.
• Segmented sending over days: When warming a subdomain, distribute your sends of engaged users over 2-3 days, gradually introducing more segments. For instance, send to active users on day one, then active plus lapsing on day two, and so on.
• Permission-based sending: Even in B2B, ensure your contacts have provided clear permission to receive your emails. Relying on not getting blocked rather than legitimate permission is a risky strategy for long-term deliverability.
• Monitor domain reputation: Regularly check your domain's reputation with tools like Google Postmaster Tools. A new subdomain will start with no reputation, so consistent positive engagement is key to building it up. Learn more in our guide on understanding your email domain reputation.

Key findings

• Reputation building: New subdomains lack a sending history, meaning they have no reputation. The warm-up process is primarily about building a positive reputation with ISPs through consistent, desired email interactions.
• Gradual increase: A phased approach to sending volume is a cornerstone of warm-up. Sudden spikes in volume from a new or cold sender are highly scrutinized and often lead to throttling or blocking.
• Engagement signals: Documentation emphasizes that positive engagement (opens, clicks, replies) helps build trust, while negative signals (complaints, bounces, spam trap hits) severely harm reputation. This highlights the importance of sending to highly engaged lists during warm-up.
• DNS configuration: Setting up a subdomain for email requires proper DNS records, including SPF, DKIM, and DMARC, to authenticate your sends and prove legitimacy. Without these, even a perfectly warmed domain can fail deliverability. You can use our free DMARC record generator tool to assist with this.
• Monitoring vital: Continuous monitoring of deliverability metrics and sender reputation using tools like Google Postmaster Tools or your ESP's analytics is crucial to adapt your sending strategy. Regular blocklist checks are also essential.

Key considerations

• Start with best contacts: Always begin your warm-up by sending to your most engaged and active subscribers who are highly likely to open and click your emails. This immediately establishes positive sending patterns.
• Pacing for deliverability: Maintain consistent sending volumes and frequencies once warm-up is complete. Erratic sending can trigger filters, even for a well-established subdomain.
• Quality over quantity: For B2B, focus on sending valuable content to relevant contacts rather than simply maximizing volume. A smaller, highly engaged list will yield better deliverability outcomes than a large, unengaged one.
• Authentication standards: Ensure your new subdomain has correctly configured SPF, DKIM, and DMARC records. These are fundamental for email authentication and prove that you are an authorized sender for that domain.
• Adherence to guidelines: Follow guidelines provided by major mailbox providers (e.g., Google, Microsoft, Yahoo) for new senders, as these outline their expectations for building and maintaining sender reputation. For instance, most domains can be warmed up within 3-6 weeks, though for larger sends this may extend to 3 months.