How can I assess deliverability health for prospective email marketing clients?
Michael Ko
Co-founder & CEO, Suped
Published 26 May 2025
Updated 16 Aug 2025
7 min read
When taking on new email marketing clients, one of the first and most critical steps is to assess their existing email deliverability health. I want to understand what I'm stepping into and identify potential red flags before committing to a partnership. This initial assessment helps set realistic expectations, scope the work accurately, and avoid inheriting major deliverability problems that could undermine my efforts.
It's not just about looking at a few numbers, it's about understanding the entire sending ecosystem, from technical setup to content practices and audience engagement. A thorough pre-assessment can save a lot of headaches down the line and ensure that your strategies will actually reach the inbox. It's about due diligence, both for your reputation and your client's success.
While some aspects of a full deliverability audit might require a deeper dive and access to client-specific data, there's a lot I can uncover with publicly available information and strategic questioning. My goal is always to get a high-level understanding of their current state and identify any immediate concerns that could indicate a troubled sender reputation or a history of deliverability issues.
Initial assessment: what to look for at a glance
Before even speaking with a prospective client, I start by gathering publicly available information. This often involves subscribing to their newsletters, registering on their website, and observing the types of emails they send. This allows me to see the email content, sender identity, and where their emails land in my own inbox. Are they going to the primary inbox, promotions, or even spam? This simple step provides invaluable first-hand insight into their current inbox placement.
I also check their domain and IP addresses against common public blocklists (or blacklists). Being listed on a major blocklist can severely impact deliverability, leading to emails being rejected or sent straight to spam folders. While this isn't the sole indicator of health, it's a significant red flag that requires immediate attention and investigation. You can check this by reviewing various blocklist databases using a tool like the MXToolbox SuperTool. This will show you a list of blocklists their domain or IP might be on.
Common red flags
Poor inbox placement: Emails consistently landing in spam or promotions folders.
Missing or incorrect authentication: Lack of SPF, DKIM, or DMARC records.
Blacklist presence: Domain or IP listed on major public blocklists.
High bounce rates: Indicating an unmaintained or old email list.
Another quick check involves their domain's email authentication records: SPF, DKIM, and DMARC. These records are fundamental to establishing sender legitimacy and preventing spoofing. You can look up these DNS records using public tools. Missing or improperly configured records are a sign of poor technical hygiene and often correlate with deliverability problems. A strong DMARC policy, for example, indicates a proactive approach to email security.
Once initial observations are made, a more technical audit of their email infrastructure becomes necessary. This includes thoroughly checking their SPF, DKIM, and DMARC records beyond just their existence. I look for proper configuration, alignment, and any errors that might be causing authentication failures. Misconfigurations can severely hurt their sender reputation and deliverability. It's crucial to understand a simple guide to DMARC, SPF, and DKIM.
Example DMARC recordtext
_dmarc.yourclientdomain.com. IN TXT "v=DMARC1; p=quarantine; rua=mailto:reports@yourclientdomain.com; ruf=mailto:forensics@yourclientdomain.com; fo=1; aspf=s;"
I also pay close attention to their sender IP address and domain reputation. Mailbox providers like Gmail and Outlook use these reputations to decide whether to accept or reject emails. A poor reputation indicates past sending practices that have triggered spam filters. While tools exist to monitor these, some data is proprietary to the ISPs. You can gain some insight into how to improve email IP and domain reputation.
Understanding their sending volume and frequency is also key. Sudden spikes in volume, or very inconsistent sending patterns, can trigger spam filters, even for legitimate senders. This data usually needs to be provided by the client, as it's not publicly available, but it's a critical component of assessing their current standing.
Technical aspects
Authentication records: Verify SPF, DKIM, and DMARC setup and alignment.
IP and domain reputation: Check public records and ask for ISP feedback loop data.
Mail server configuration: Ensure proper DNS, reverse DNS, and SMTP settings.
Sending volume: Analyze consistency and spikes in email sending.
Systemic (non-technical) aspects
List acquisition practices: Understand consent, opt-in methods, and list hygiene.
Engagement metrics: Review opens, clicks, bounces, complaints, and unsubscribes.
Content relevance: Assess email content for spam trigger words and personalization.
Subscriber management: Evaluate how inactive subscribers and bounced addresses are handled.
Understanding engagement and sender reputation
Beyond technicalities, client engagement metrics are paramount. I request access to their historical email performance data, focusing on metrics like open rates, click-through rates, bounce rates (hard and soft), spam complaint rates, and unsubscribe rates. Low engagement, high bounces, or elevated complaint rates are strong indicators of list quality issues or irrelevant content. A low spam complaint rate is crucial for healthy deliverability.
Metric
What it tells you
Ideal range/What to look for
Open Rate
Indicates content relevance and subject line effectiveness.
Generally 20%+
Click-Through Rate (CTR)
Shows audience engagement with your calls to action.
It's important to differentiate between hard and soft bounces. Hard bounces indicate permanent delivery failures (e.g., invalid email address) and should be removed immediately. Soft bounces are temporary issues, but if persistent, they can still negatively affect reputation. High bounce rates can signal a poorly maintained list or bad acquisition practices. Understanding how to accurately test and measure email deliverability relies heavily on these metrics. For further context, the Kickbox Email Deliverability report states that poor deliverability significantly impacts revenue.
Finally, I delve into their list acquisition practices. How do they collect email addresses? Are they using single opt-in, double opt-in, or something less compliant? Are they purchasing lists, which is a major red flag? Poor list hygiene, such as not removing inactive subscribers or not honoring unsubscribe requests, can quickly lead to blocklist appearances (or blacklists) and significant deliverability degradation. This aspect often reveals the root cause of many deliverability problems, so make sure you understand an in-depth guide to email blocklists.
Views from the trenches
Best practices
Prioritize understanding systemic issues beyond just technical configurations.
Always bill for initial discovery and audit work to value your expertise.
Ask probing questions about their email acquisition methods and list management.
Subscribe to their email lists to observe their sending practices firsthand.
Common pitfalls
Solely relying on free tools for a comprehensive deliverability assessment.
Ignoring non-technical issues like poor consent practices or list hygiene.
Underestimating the time and effort required for thorough client qualification.
Not charging for initial investigative work, leading to undervalued services.
Expert tips
Utilize advanced paid tools for in-depth deliverability and inbox placement insights.
Review client credit history as an additional layer of due diligence.
Trust your intuition if a prospective client seems problematic or unwilling to cooperate.
Seek historical email performance metrics directly from the client to gauge their past performance.
Expert view
Expert from Email Geeks says that assessing a client's deliverability health should be considered a billable service.
Aug 11, 2021 - Email Geeks
Marketer view
Marketer from Email Geeks suggests subscribing to a prospect's emails to directly observe their practices, noting that paid tools offer deeper insights.
Aug 11, 2021 - Email Geeks
A holistic approach to client assessment
Assessing a prospective client's deliverability health is a multifaceted process that combines technical analysis, data review, and insightful questioning. It's about piecing together a comprehensive picture to understand their current state and identify underlying issues. This proactive approach ensures you can accurately gauge the effort required to improve their deliverability and avoid unforeseen challenges.
Remember that deliverability issues are rarely singular. They often stem from a combination of technical misconfigurations, poor sending practices, and low engagement. By systematically evaluating each area, you can identify the root causes and develop a robust strategy for improvement. This rigorous assessment establishes trust and positions you as a knowledgeable partner.
Ultimately, a thorough deliverability assessment protects both you and your client. It allows you to enter partnerships with clear expectations, a defined scope of work, and the confidence that you can genuinely help them achieve better inbox placement. Neglecting this crucial step can lead to frustration, missed targets, and a damaged reputation for everyone involved. Learn more about why your emails are going to spam.
MXToolbox SuperTool. This will show you a list of blocklists their domain or IP might be on.
Gmail and 
Outlook use these reputations to decide whether to accept or reject emails. A poor reputation indicates past sending practices that have triggered spam filters. While tools exist to monitor these, some data is proprietary to the ISPs. You can gain some insight into how to improve email IP and domain reputation.
