How long did it take to create this Complete Cold Email Deliverability Guide? About 15 years. Delivering cold emails to inboxes demands extensive experience—years of testing, strategy development, evolving tactics, and countless campaigns. Mastering cold email marketing requires deep knowledge of bulk emailing, sending servers, IPs, SMTP, industry players, and spam algorithms. We’re excited to share our insights, tips, and strategies with you. Enjoy!
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Table of content
- 1. How does cold email deliverability sender reputation work?
- 2. How can email deliverability be REALLY improved?
- 3. What are the best email deliverability practices to follow?
- 4. What is the best service to use when sending cold bulk emails?
- 5. How can I send 10K cold emails per day?
- 6. How to check an email delivery campaign’s reputation?
- 7. What is the difference between email soft bounce and hard bounce?
- 8. Which is the best tool to check email deliverability score?
- 9. Is there a way to boost email reputation?
- 10. What do you mean by email deliverability service, and what are the advantages of B2B email deliverability services?
- 11. What does it mean when your email has low deliverability?
- 12. What are the benefits of Email Deliverability services?
- 13. Does linking my website in a cold email look like spam?
- 14. Given the effectiveness of spam filters, is cold emailing 'over'?
- 15. Is cold email spam?
- 16. What is the best service to use when sending cold bulk emails, and what is the best platform to send cold emails from?
- 17. How can I detect spam traps among my user list?
- 18. What is the best tool for cold email marketing?
- 19. How can email deliverability be improved, and How to deal with email deliverability issues?
- 20. What is a dedicated IP in email marketing?
- 21. Do I need a shared IP or a dedicated IP for my email marketing?
- 22. In email marketing, what is an IP warm-up?
What is The Main Challenge in Cold Emailing?
The main challenge when applying cold email practices is deliverability—your ability to deliver emails to your recipients’ inboxes while avoiding spam filters. In other words, if your deliverability is strong, your ability to reach new audiences through cold emails is high.
How Do Spam Filters Work?
It’s crucial to understand how email spam filters operate and how to validate your sending servers to ensure your campaigns are delivered. Internet Service Providers (ISPs) work to detect bot-generated emails and either remove them from primary inboxes or send them directly to spam folders. When mass emails are sent to a large number of recipients from a new IP address, it can raise red flags. To ensure your emails land in recipients’ inboxes, you must first build a good reputation with ISPs. Simply put, make your emails appear human.
This sender reputation is often referred to as email validation.
How Does Sender Reputation Affect Cold Email Deliverability?
Cold email deliverability refers to your email campaigns’ ability to reach the inbox. Email deliverability heavily depends on sender reputation, a rating given by each mailbox provider or ISP (like Gmail, Yahoo, or Hotmail). Sender reputation reflects the level of trust you, the sender, have with each ISP. This trust is determined by various factors, including the campaign history of your IP, the domain used to send the emails, the URLs linked in the emails, the content of the emails, and more.
How Can Email Deliverability Be Truly Improved?
First and foremost, email deliverability can be improved by enhancing the reputation of the server or IP used to send your emails. However, if you’re in the cold email business, it’s almost inevitable that your IP will eventually be flagged. Someone who didn’t request your campaigns will report your emails.
Here are some common practices and why they often fail with bulk cold emails:
Conventional Email Platforms with Shared IPs
This is likely the first approach you tried—signing up with platforms like ActiveCampaign, Brevo, MailerLite, or ConvertKit and using their shared IPs, which are generally strong and reliable. However, besides the high costs associated with these platforms, if they detect that you’re running cold campaigns (e.g., uploading large databases and showing low open rates), they will likely suspend your account. Why? Because their shared IP reputation is maintained by not allowing cold emails.
Dedicated IPs and Servers like Postmark
After realizing that shared IPs are unsuitable for cold emails, you might be advised to get a dedicated IP. Brevo might suggest this quickly, ActiveCampaign might direct you to Postmark—an email delivery service they acquired—and other platforms might recommend services like Contabo or DigitalOcean. The costs of these dedicated IPs are high, and they require a proper warm-up to deliver bulk emails effectively, making this option costly and often impractical. Additionally, like shared IPs, if you experience hard bounces, complaints, or flagging of your cold emails, providers like Postmark and Contabo will almost certainly suspend your account. That’s a 100% guarantee.
Systems with External Mailboxes
These systems are designed to allow you to connect a variety of external senders, such as SMTP services, cloud-based email servers, and other third-party mailboxes. They offer the flexibility to manage your sending infrastructure without relying on a single platform’s IP reputation. However, this approach comes with its challenges: managing multiple mailboxes, maintaining consistent email authentication (SPF, DKIM, DMARC), and navigating deliverability risks with each external sender. Without rigorous setup and monitoring, these systems can still face deliverability issues, as any flagged sender can negatively impact your entire campaign’s success.
Then what are the best email deliverability practices to follow?
There are many strategies for cold emailing, and they evolve as often as spam algorithms change—which is all the time. However, here’s what we currently do to optimize deliverability:
Rotating Senders (Domains and IPs): We rotate multiple sending domains and IP addresses to distribute the email load and maintain a healthy reputation across various servers.
Use Mailboxes from Different Providers: We diversify by using mailboxes from Google Workspace, Outlook, Mailgun, VPS providers, and more. This reduces the risk of any single provider flagging or blocking our campaigns.
Warm Up SMTP Servers: We warm up our SMTP servers for at least two weeks to establish trust and build sender reputation gradually, reducing the chances of landing in spam folders.
Start with Plain Text Emails: The first email is always text-only—no links or images. This approach lowers the spam score and helps establish initial engagement with recipients.
Connect to a Warm System: We link our emails to a warming system, allowing us to move engaged recipients into more nurturing drip campaigns, gradually introducing links and richer content.
Immediate Bounce Management: We remove hard bounces immediately to maintain a clean list and protect our sender reputation from damage caused by invalid addresses.
Authenticate Your Emails (SPF, DKIM, DMARC): Properly set up email authentication protocols like SPF, DKIM, and DMARC to prove your emails are legitimate and not spoofed, helping to improve inbox placement.
Monitor Engagement Metrics: Track open rates, clicks, replies, and other engagement metrics to identify and remove non-engaged contacts, focusing your efforts on recipients who show interest.
Personalize Emails: Even at scale, adding elements of personalization can improve engagement rates and signal to ISPs that your emails are relevant and wanted.
Regularly Clean Your Lists: Regular list hygiene, including verification and removing inactive contacts, keeps your sending reputation high and minimizes the risk of being flagged as spam.
Copywriting/Content Strategy
As far as the content of your emails goes, remember: the more relevant your emails are to the recipients, the higher the chances of avoiding spam filters. Here are some high-performing strategies to consider:
Engaging Subject Line and Preview Text: Your subject line is the first impression—make it engaging and enticing enough to encourage opens. Use preview text to complement your subject line and hint at the value inside.
Segmentation: Segment your lists to tailor personalized messages. This strategy allows you to send highly relevant content to specific audience groups, increasing engagement and reducing the risk of being marked as spam.
Keep an Engaging Signature: An engaging, professional signature adds credibility to your emails and can include subtle elements that reinforce your brand’s identity.
Avoid Linking to Flagged Sites: Links to flagged or low-reputation sites can harm your deliverability. Always ensure that your links lead to reputable, trustworthy domains.
Remove Spammy Words: Avoid using words and phrases commonly flagged as spam, such as “free,” “urgent,” and “limited-time offer.” These can trigger spam filters and lower your deliverability.
Add Real Value to the Reader: Make sure your emails provide real worth to the reader. The content should be useful and engaging on its own, making the reader feel rewarded just by reading your email.
First Email Structure:
Excuse: Start with a personalized opener, such as “I came across your profile,” “I saw your content on…,” or “I found your work on…”. This approach establishes a genuine reason for reaching out.
Why I Contacted You: Clearly state the purpose of your email—how you can help, what problems you solve, or share relevant examples. This section should immediately highlight the benefit to the recipient.
Credibility: Build trust by mentioning similar clients or recent successes, such as “Recently, we helped [Client] achieve [result].” Demonstrating proven results boosts your credibility.
Soft CTA: Use a non-intrusive call-to-action, like “Mind if I send you more info?” This keeps the engagement light and invites further communication without pressure.
About the Subject Line:
Avoid Generic Phrasing: Avoid subject lines that are vague or overused. The more personalized and specific your subject line, the higher the chances your email will be opened.
Speak Directly to the Reader: Include personalized details that reflect something about the reader, making the email feel relevant and tailored specifically to them.
Example:
Recently, we sent cold emails for a client targeting over 100,000 Instagram influencers in a specific niche.
Our strategy included adding each influencer’s follower count to the subject line. For instance, we used, “@… 56,644 followers and counting!”
This simple tweak made the subject line highly personalized and relevant, leading to an open rate that went through the roof.
What is the best service to use when sending cold bulk emails?
While email marketing platforms like ActiveCampaign, Brevo, or MailerLite are excellent for nurturing existing subscribers, they are not designed for cold bulk emailing. These platforms rely on shared IPs with strong reputations, and they protect these reputations fiercely. If they detect cold emailing activities—such as low engagement rates, high bounce rates, or spam complaints—they will suspend your account to prevent damage to their shared IP deliverability. Their business model and policies prioritize email marketing to consent-based lists to maintain their IPs’ integrity and performance, making them unsuitable for cold outreach.
Context:
Conventional email marketing tools are optimized for campaigns targeting existing customers or subscribers who have explicitly opted in to receive communications. These tools employ robust spam filters, sophisticated tracking, and reputation management systems to protect their sending infrastructure. As a result, any hint of cold emailing activity is quickly flagged and penalized, often resulting in account suspension or termination.
Cold Email Tools:
Now, let’s look at tools specifically designed for cold emailing, such as Apollo, Woodpecker, Saleshandy, Hunter.io, and Instantly. These tools excel at cold outreach, allowing you to connect multiple mailboxes from various providers, manage large email lists, and send personalized cold emails at scale. They are built to support cold emailing and offer functionalities that align well with initial outreach efforts.
However, they fall short in key areas:
Limited Drip Campaign Options: These tools lack advanced features for creating sophisticated drip campaigns with complex conditions, tagging, and event-based actions. For example, if a prospect replies to an email, you may want to automatically remove them from a cold drip and move them into a different nurture sequence. These nuanced automations are crucial for maintaining an organized and responsive sales process.
Integration with CRMs and Marketing Platforms: Cold email campaigns are often just the first step in a broader sales funnel. After engaging a prospect, you’ll want to transfer them into a CRM or marketing platform where you can further nurture them—via SMS, phone calls, advanced drip sequences, and sales opportunity tracking. Unfortunately, tools like Apollo and Woodpecker often require external integrations through services like Zapier to connect to your CRM. These integrations can be limited, unreliable, or insufficient, hindering the seamless transition of leads through your sales funnel.
This is where Omnily.io stands out as the best tool for cold emailing:
Unlimited Sending Domains: You can connect as many sending domains as needed, ensuring that your campaigns remain diverse and reputable.
Direct Domain Acquisition: Omnily.io even allows you to acquire domains directly from within the system, streamlining your setup and reducing external dependencies.
Dynamic IP and Domain Rotation: The system automatically swaps and rotates sending domains, ensuring that they do not exceed their sending quotas, maintaining a healthy reputation. You can utilize up to 100 domains or more as needed.
Advanced Drip Campaign Options: Omnily.io offers an abundance of drip campaign features, including conditional logic, tagging, event-based triggers, and automatic workflows that adjust based on prospect engagement. (Add specific features from Omnily.io here.)
Unlimited Data and Sending Capabilities: No caps on data or email sends, allowing you to scale your outreach without restrictions.
Integrated CRM Functionality: Your cold email tool doubles as your CRM, with built-in features that include contact management, task automation, lead nurturing, SMS and call capabilities, and comprehensive sales tracking. (Add more CRM features from Omnily.io here.)
In-System Address Verification: Verify email addresses directly within Omnily.io, ensuring your lists are clean and reducing the risk of hard bounces.
End-to-End Sales Process Management: Omnily.io seamlessly integrates cold emailing with full sales cycle management, helping you move prospects from initial contact to sales opportunities without losing momentum.
With Omnily.io, you have a fully integrated cold email and CRM platform designed to manage your entire outreach and sales process efficiently. It combines the best of cold emailing tools with advanced CRM capabilities, making it the ultimate choice for scaling your business outreach efforts.
How can I send 10K cold emails per day?
We recommend the following practice to get the best deliverability when sending 10K cold emails per day:
* 4-5 rotating IPs
* 3 Rotating sending domains
* Warm up your servers
Read here a full comparison of the best bulk email platforms
How to Check an Email Delivery Campaign’s Reputation?
Check Hard Bounce Rates
An email bounces when the ISP (e.g., Gmail, Yahoo, etc.) or the server returns the email without delivering it. A hard bounce usually occurs when the address is incorrect or there is another permanent issue with the address. Hard bounces harm your sender reputation, so you should avoid them by verifying all addresses before emailing them.Check Complaint Rates
Monitor the number of complaints your campaign receives, as high complaint rates can negatively impact your sender reputation.Check Your Opening Performance and Campaign Stats Regularly
If your open rate is sufficient, your emails are likely reaching the inbox rather than the spam folder, which is great news. However, if your click rate is low, it means people are opening your emails but not engaging further. This could indicate that your content needs improvement, or that your messages should be more segmented and relevant.
If there are no bounces or spam reports but open rates are low, your subject line might not be strong enough, or your content might not resonate with your audience. Understand your audience, learn what they need, and use your emails to communicate with them on a level that is valuable to them.Send Tests to Multiple Email Addresses and Check the Delivery Tabs
Send test emails to multiple addresses to see where they land—in the primary inbox, promotions, or spam folder. This will help you adjust your content and sending strategy to improve deliverability.
What is the difference between an email soft bounce and a hard bounce?
A soft bounce occurs when an email reaches the destination server but is not delivered to the recipient’s inbox, often because the inbox is full, temporarily unavailable, or inactive. Soft bounces do not significantly harm your sender reputation.
Hard bounces, on the other hand, are detrimental to your sender reputation. They indicate a permanent error, such as an incorrect or non-existent address, preventing the email from being delivered. To avoid hard bounces, ensure you clean and verify your email lists before sending cold campaigns.
Which is the best tool to check email deliverability score?
ZeroBounce Score™ is a tool that uses artificial intelligence to assess how your subscribers may interact with your cold emails. By detecting email activity levels, the tool can indicate how likely you are to reach a real person on the other end of an email. The scores range from 0 to 10, with 10 being the highest quality rating.
Is there a way to boost email reputation?
The strategy that the team at Omni Online Strategies has developed to boost email reputation consists of:
3 Main IPs that are kept clean, active, and validated. These IPs are used to send emails to your best contacts—those who consistently engage and trust your messages.
28 Warm-Up IPs used to send initial emails, identify bounces, and remove unengaging contacts. The purpose of these IPs is to filter and identify the most responsive contacts in your lists. Once identified, these high-quality contacts are moved to the Main IPs for continued communication. The aim is to keep these Main IPs healthy and maintain a high sender reputation. While the warm-up IPs may eventually get burned and go out of use, by that time, you should have built a clean, verified, and segmented list of engaged recipients who know you, trust your emails, and respond to your messages.
Deep Segmentation of contact lists allows for personalized, valuable communication, leading to higher engagement and improved sender reputation.
