Summary
When initiating cold email campaigns from a new domain, email warmup is not just recommended, but overwhelmingly considered essential. This crucial process involves gradually increasing sending volumes to build a positive sender reputation with Internet Service Providers (ISPs). Skipping warmup for a fresh domain can lead to immediate classification as spam, blacklisting, or severe deliverability issues, as ISPs view sudden, high-volume sending from unknown domains as highly suspicious. While some views suggest avoiding cold emails entirely or offer harmful, sarcastic advice about bypassing deliverability rules, the consensus among marketers and documentation from major providers like Google, Microsoft, and Zoho Mail firmly supports the necessity of a methodical warm-up strategy.
Key findings
- Warmup is Essential: For new domains, particularly when used for cold emailing, email warmup is universally deemed a non-negotiable step to ensure deliverability and avoid immediate placement in spam folders or blacklisting.
- Builds Sender Reputation: The primary purpose of email warmup is to establish a positive sending history and reputation with Internet Service Providers, a critical factor for emails reaching the inbox.
- Prevents Spam & Blacklisting: Launching cold email campaigns from an unwarmed domain typically results in immediate detection as suspicious activity by ISPs, leading to high spam rates, domain blocking, or outright blacklisting.
- Requires Gradual Volume Increase: Effective warmup involves starting with very low email volumes and slowly increasing them over time, demonstrating legitimate sending patterns to email providers.
- Critical for Cold Outreach: Due to the nature of cold emails, the need for domain warmup is even more pronounced, as it lays the foundation for maintaining deliverability and preventing domain burnout in outreach efforts.
Key considerations
- Start Small, Target Engaged: Begin your warmup by sending low volumes of emails, ideally to highly engaged recipients, and progressively scale up to build trust with ISPs.
- Prioritize Consistency: Maintain consistent and legitimate sending patterns throughout the warmup period to signal reliability and avoid triggering spam filters, which see sudden volume spikes as red flags.
- Invest in Domain Health: View email warmup as a foundational investment in your domain's long-term health and deliverability, ensuring future campaigns have a higher chance of inbox placement.
- Dismiss Harmful Advice: Beware of and disregard any advice suggesting that warmup is unnecessary or that recommends risky practices like disabling DMARC for cold emails, as such approaches lead to immediate and severe deliverability penalties.
- Align with ISP Guidelines: Recognize that the principles of email warmup align directly with best practices advised by major email providers like Google, Microsoft, and Zoho Mail for new domains, emphasizing slow, reputation-building activity.
What email marketers say
11 marketer opinions
There is a strong consensus among email marketing experts that warming up a new domain is a critical, non-negotiable step before initiating cold email campaigns. This process is deemed essential to establish a positive sender reputation with Internet Service Providers (ISPs), which helps ensure emails reach the inbox rather than the spam folder. Without proper warmup, a new domain sending a sudden surge of cold emails is highly likely to be flagged as suspicious, leading to immediate blacklisting, high spam rates, or complete domain blocking. While one perspective suggests avoiding cold emails altogether, the prevailing expert opinion firmly underscores the necessity of a methodical domain warmup strategy for anyone engaging in this form of outreach.
Key opinions
- Mandatory for New Domains: Email warmup is considered an absolute requirement for new domains, especially when used for cold email outreach, with experts calling it non-negotiable and foundational.
- Builds Sender Reputation: The primary objective of warming up a domain is to gradually establish a positive sending history and build trust with Internet Service Providers (ISPs).
- Prevents Spam & Blacklisting: Skipping warmup almost invariably leads to emails being routed directly to the spam folder, domain blacklisting, or severe deliverability issues due to ISPs flagging sudden high-volume sending as suspicious.
- Establishes Credibility: Warmup acts as a signal of legitimacy to email providers, helping them recognize the new domain as a trustworthy sender over time.
- Ensures Inbox Placement: By building reputation and trust, warmup significantly increases the likelihood that cold emails will bypass spam filters and successfully reach recipients' inboxes, protecting overall deliverability and preventing domain burnout.
Key considerations
- Gradual Volume Ramp-Up: Implementing a slow and steady increase in email sending volume is crucial, as this phased approach helps ISPs gradually accept and trust the new domain.
- Prioritize Domain Trust: View email warmup as an essential investment in building the domain's credibility and long-term health, directly impacting future campaign success.
- Avoid Immediate High Volume: Refrain from sending large volumes of emails immediately from a fresh domain, as this behavior is a primary trigger for spam filters and domain suspension.
- Consider Dedicated Tools: Many experts recommend using specialized email warmup services to automate and manage the reputation-building process effectively.
- Understand Cold Email Nuances: While warmup is vital, remember that cold emailing itself carries inherent deliverability challenges; warmup is the critical first step but not the sole guarantee for success in this specific outreach method.
Marketer view
Marketer from Email Geeks explains that cold emails should not be sent, regardless of whether a warmup process is performed.
6 Feb 2023 - Email Geeks
Marketer view
Email marketer from Mailshake explains that email warmup is absolutely necessary for new domains, especially for cold emailing, to build a positive sending history and reputation with ISPs, thus bypassing the spam folder.
17 Mar 2025 - Mailshake Blog
What the experts say
3 expert opinions
For new domains engaging in cold email outreach, the process of email warmup is unanimously considered essential by deliverability experts. A new domain lacks any established sending history, and attempting to send a large volume of emails immediately will invariably trigger spam filters, leading to deliverability failures. The purpose of warmup is to progressively build a positive sender reputation with Internet Service Providers by gradually increasing email volume, beginning with highly engaged recipients, thereby establishing the domain's legitimacy and trustworthiness over time. Ignoring this crucial step based on misguided or harmful advice will severely impair email deliverability.
Key opinions
- Warmup is Indispensable: New domains starting cold email outreach absolutely require a methodical warmup process to avoid being immediately flagged by spam filters.
- Reputation Building is Key: The core function of email warmup is to establish and build a positive sender reputation for a new domain that lacks any prior sending history.
- Prevents Spam Triggers: Sending high volumes from a fresh domain without prior warmup immediately signals suspicious activity to Internet Service Providers, leading to deliverability failures.
- Gradual Volume Increase: An effective warmup strategy involves a methodical, slow increase in sending volume, initially targeting highly engaged recipients to build trust with email providers.
- Essential for Inbox Placement: Proper email warmup significantly increases the likelihood that emails from new domains will bypass spam filters and successfully reach recipients' inboxes, protecting overall deliverability.
Key considerations
- Establish Trust Gradually: Prioritize building a positive reputation over rapid sending volumes, understanding that trust takes time for new domains.
- Focus on Engaged Recipients: Begin the warmup process by sending to a small segment of highly engaged recipients to secure positive engagement signals with ISPs.
- Understand Reputation's Role: Recognize that a domain's sender reputation is paramount; without it, emails from new domains will struggle to reach the inbox.
- Reject Harmful Strategies: Disregard any advice suggesting shortcuts like disabling security protocols such as DMARC or using generic sender addresses, as these approaches are detrimental to deliverability.
- Invest in Long-Term Deliverability: View email warmup as a foundational step for sustained email success and healthy deliverability, not merely a temporary hurdle for initial cold outreach.
Expert view
Expert from Email Geeks shares sarcastic, harmful advice, suggesting that warmup is not needed for cold emails, and recommends methods like disabling DMARC and sending from noreply addresses to avoid rejections.
25 Nov 2021 - Email Geeks
Expert view
Expert from Spam Resource explains that warming up a new email address or domain is essential because new IPs and domains lack a sending reputation. Sending a large volume of mail immediately from a new, cold domain will likely trigger spam filters. A gradual increase in sending volume, starting with engaged recipients, is necessary to build a positive reputation and improve deliverability.
3 Mar 2024 - Spam Resource
What the documentation says
5 technical articles
Major email providers and deliverability experts consistently emphasize that for new domains, particularly those used for cold email outreach, a strategic approach to building sender reputation is absolutely vital. While not always explicitly termed 'warmup,' documentation from Mailgun, Google, Microsoft, Proofpoint, and Zoho Mail outlines a process that mirrors it exactly: starting with low email volumes, gradually increasing them, ensuring high engagement, and maintaining consistent sending patterns. This methodical approach is crucial for new domains to establish trustworthiness with Internet Service Providers and avoid being immediately flagged as suspicious, which would lead to poor deliverability or blacklisting.
Key findings
- Reputation is Crucial: Building a positive sender reputation is consistently highlighted by Mailgun, Google, Microsoft, and Zoho Mail as the most crucial aspect for new domains.
- Gradual Volume is Standard: All major providers, including Google, Microsoft, and Zoho Mail, emphasize starting with low email volumes and gradually increasing them for new domains.
- Functions as Warmup: The recommended practices by ISPs, such as starting low, increasing volume, and ensuring engagement, effectively serve as a necessary warm-up process for new domains.
- Consistency Prevents Flags: Proofpoint specifically notes that establishing consistent sending patterns and avoiding sudden volume spikes is critical for reputation management and to prevent new domains from being flagged as spam.
- Engagement is Key to Trust: High engagement rates are vital for new domains, as they signal legitimate activity and help build trust with email filters and receiving servers.
Key considerations
- Start with Low Volume: For new domains, begin by sending a small volume of emails and gradually increase it over time to allow email providers like Google and Microsoft to build trust.
- Focus on Engagement: Ensure that the initial emails sent generate positive engagement signals, which helps solidify a good sender reputation with services such as Mailgun and Zoho Mail.
- Maintain Consistency: Establish consistent and legitimate sending patterns, avoiding sudden spikes in volume from a new domain to prevent triggering spam filters, as highlighted by Proofpoint.
- Avoid Spam Traps: Actively work to avoid spam traps and other negative signals that could quickly damage the nascent sender reputation of a new domain.
- Align with ISP Guidelines: Recognize that the principles of email warmup are directly aligned with the guidelines from major ISPs for new domains and IPs, focusing on careful, reputation-building practices.
Technical article
Documentation from Mailgun explains that building a positive sender reputation is crucial for new domains, which involves sending legitimate emails, avoiding spam traps, and ensuring high engagement, effectively functioning as a warm-up process.
6 Aug 2022 - Mailgun Documentation
Technical article
Documentation from Google explains that senders, particularly those using new domains, should start with low email volumes and gradually increase them to build a positive sender reputation with Gmail's filters.
22 Feb 2024 - Google Postmaster Tools Help
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