What are the challenges of working with cold email senders and deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 22 Apr 2025
Updated 16 Aug 2025
6 min read
Working with cold email senders on deliverability can feel like navigating a minefield. While cold outreach is a popular sales and marketing strategy, its very nature often conflicts with the principles of good email deliverability. The core issue boils down to recipient consent and the expectations of mailbox providers (ISPs).
Unlike transactional or marketing emails sent to opted-in subscribers, cold emails are unsolicited. This fundamental difference creates a challenging environment where standard deliverability best practices are difficult, if not impossible, to apply effectively. Senders often seek quick fixes or magic bullets, but the underlying problem is systemic.
My experience has shown that addressing cold email deliverability is less about tweaking technical settings and more about fundamentally changing the approach to recipient engagement and list acquisition. Without this shift, senders will continue to face an uphill battle against spam filters and reputation damage.
The fundamental challenge: recipient consent and sender reputation
The primary challenge in cold email deliverability stems from its very definition: sending emails to recipients who haven't explicitly asked for them. This immediately puts the sender at a disadvantage in the eyes of internet service providers (ISPs) and spam filters. ISPs prioritize user experience, and unsolicited emails often lead to negative engagement signals such as low open rates, high delete-without-reading rates, and, most critically, spam complaints.
Each negative signal erodes the sender's reputation, making future emails even less likely to reach the inbox. If enough negative signals accumulate, the sending IP address or domain can end up on a public or private blacklist (or blocklist), effectively blocking all outgoing mail. Recovering from a poor sender reputation, especially after sending cold emails, is a prolonged and difficult process.
Furthermore, mailbox providers like Google and Yahoo have recently implemented stricter sender requirements, emphasizing authentication and low spam complaint rates. These changes disproportionately impact cold email senders, who inherently struggle to meet these new thresholds. The rules are designed to protect recipients from unwanted mail, making it harder for cold outreach to succeed.
The cold email dilemma
Cold email aims for unsolicited outreach, which directly conflicts with ISP policies favoring consent and positive engagement. Even technically perfect emails will struggle if recipients mark them as spam.
Poor sender reputation is a common outcome, leading to lower inbox placement and potential blacklisting (blocklisting). Recovering from this is a long-term commitment that often requires abandoning cold email practices.
The pitfalls of poor data quality and list acquisition
Another significant hurdle for cold email senders is the quality of their recipient lists. Unlike opted-in lists which are regularly maintained and updated, cold email lists are often acquired from third-party sources, scraped from the internet, or compiled without direct verification. This leads to a high percentage of invalid, outdated, or risky email addresses.
Sending to invalid addresses results in high bounce rates, which are a major red flag for ISPs and severely damage sender reputation. Worse still, these lists often contain spam traps. Spam traps are email addresses designed to catch unsolicited senders. Hitting one immediately signals to ISPs that you are sending spam, often leading to immediate blacklisting (blocklisting) or severe throttling.
Even if a list is seemingly clean, the lack of engagement from cold recipients can itself be a deliverability issue. Low open rates, low click-through rates, and high unsubscribe rates tell ISPs that your content isn't relevant to recipients, contributing to a declining sender reputation. This is why cold email delivers so many challenges.
Good list practices
Consent-based acquisition: All recipients have explicitly opted-in to receive your emails, usually through a double opt-in process.
Regular cleaning: Continuously remove bounces, inactive users, and suppress unsubscribes.
Segmented engagement: Tailor content to specific segments to maximize relevance and engagement.
Technical hurdles and authentication
While technical email authentication protocols like SPF, DKIM, and DMARC are crucial for deliverability, they alone cannot overcome the inherent challenges of cold email. These protocols help mailbox providers verify that an email is legitimate and hasn't been tampered with. However, even perfectly configured authentication won't guarantee inbox placement if other sender reputation factors are poor.
For cold emailers, it's common to use newly warmed-up domains or separate domains to protect their main brand. While this can mitigate immediate damage to the primary domain, these new domains still need to build their own reputation. This often involves a careful IP warmup process, which large sends often lack. Attempting to send high volumes of unsolicited mail from a new domain or IP will quickly result in reputation damage and blocklisting.
Implementing DMARC with a policy of p=reject is a strong signal of legitimacy. However, DMARC works best when coupled with a positive sender reputation and genuine engagement. For cold email, even with perfect technical alignment, the lack of consent often overrides these technical signals, leading to messages being filtered to the spam folder despite passing authentication checks.
The content and volume of cold emails also pose significant deliverability challenges. Cold emails are often generic, lacking personalization, and use sales-oriented language that can trigger spam filters. While marketers might think they are being clever, ISPs have advanced algorithms to detect such patterns, regardless of technical setup.
Sending high volumes of cold emails, even with multiple domains and IPs, is another red flag. ISPs are designed to detect mass unsolicited mailings, which can lead to throttling, filtering, or outright blocking. The cumulative effect of these challenges makes cold email deliverability an ongoing battle against the very systems designed to protect inboxes from spam. It underscores why email deliverability is a complex issue.
Views from the trenches
Best practices
Always prioritize building an opt-in list, as it forms the bedrock of good deliverability.
Segment your audience and personalize content as much as possible, even for initial outreach.
Regularly monitor your sender reputation using tools like Google Postmaster Tools.
Start with low sending volumes and gradually increase, especially for new domains.
Common pitfalls
Using purchased or scraped email lists, which are often riddled with invalid addresses and spam traps.
Sending generic, unpersonalized emails that lack value for the recipient.
Ignoring spam complaints and bounce rates, which are critical indicators of poor sender reputation.
Assuming that technical setup alone will solve deliverability issues for cold email.
Attempting to send high volumes from new or poorly warmed-up domains or IPs.
Expert tips
Focus on quality over quantity. A smaller, highly engaged list will always outperform a large, unengaged one.
Consider alternative outreach methods that build consent and rapport before email.
If cold email is a necessity, use a completely separate sending infrastructure to protect your main domain.
Educate clients on the realities of ISP filtering and the importance of recipient consent.
Always include a clear and easy unsubscribe option, even if it's cold email.
Expert view
Expert from Email Geeks says that dealing with cold email senders who have deliverability problems is challenging because the solutions required are often counter to their existing business model.
2022-09-16 - Email Geeks
Marketer view
Marketer from Email Geeks says that she cannot help cold email senders because her work depends on recipients wanting emails, which is not the case with cold outreach, leading to client dissatisfaction.
2022-09-16 - Email Geeks
Overcoming the cold email deliverability paradox
The challenges of working with cold email senders on deliverability are multi-faceted, stemming from a fundamental conflict between the nature of unsolicited email and the strict anti-spam measures employed by mailbox providers. While technical configurations like SPF, DKIM, and DMARC are essential, they are only part of the solution.
True deliverability success for any email program, including those that include cold outreach, hinges on building and maintaining a positive sender reputation. This requires a strong focus on list hygiene, genuine recipient engagement, and adherence to ethical email practices. Ultimately, the most effective way to ensure emails reach the inbox is to send wanted mail to willing recipients.
