Published Sep 24, 2025 ## 1\. Introduction to email deliverability Sales, marketing, and growth teams are revenue drivers — and email is one of their main channels for engaging new prospects, generating revenue, and growing the business. This playbook was developed by Amplemarket to help every sales team understand and optimize email deliverability — and unlock more business opportunities. ### 1.1 What is email deliverability? Email deliverability refers to the measure of an email’s ability to reach the recipient’s inbox without being filtered out as spam or blocked by email servers. It depends on various factors, including sender reputation, content quality, adherence to spam regulations, and other technical aspects. Good deliverability ensures high delivery rates, while poor deliverability leads to emails being bounced or diverted to spam folders, hindering effective communication. Improving deliverability can dramatically boost your outbound performance and make your revenue forecasts more realistic. ### 1.2 The difference between email delivery and email deliverability Email _delivery_ and _deliverability_ are closely related, but they aren’t the same thing. Email _delivery_ simply means that your email was accepted by the recipient’s server. _Deliverability_, on the other hand, is whether that email actually reaches the inbox instead of getting stuck in the spam folder. ### 1.3 Email deliverability definitions An email bounce happens when an email fails to be delivered to the recipient’s mailbox: - **A hard bounce** happens when an email address is permanently unavailable. - **Soft bounces** are usually temporary. - **A spam bounce** happens when an email fails to get delivered because it was filtered out by Spam filters. ### Mailboxes, domains, subdomains, & secondary domains - **Mailboxes:** These are individual email addresses associated with a domain or subdomain. - **Domains vs. subdomains:** The main domain (e.g., company.com) is typically your primary email address, while subdomains (e.g., mail.company.com) are offshoots used to separate communication channels. - **Secondary domains:** Secondary domains are entirely separate domains from your primary one. ### Reputation Every sender’s IP, domain, and individual email address has a reputation score. Actions of an individual sender will impact their own reputation but also the company’s domain and IP address reputation. Let’s dive deeper into the different aspects of reputation: - **Sender reputation:** This is the reputation of a specific mailbox/ email address from which an email is being sent. - **Domain reputation:** The aggregated reputation of individual mailboxes. - **IP address reputation:** The main difference is that several companies could be sharing the same IP address. **_Having a single dedicated IP is expensive and usually comes as an extra feature, hence most people opt to share an IP address to reduce costs._** Calculating delivery rate measures the percentage of emails that were successfully delivered to recipients’ servers. ### What is a poor deliverability rate? According to industry benchmarks, [anything below 80% should raise some flags](https://agencyanalytics.com/kpi-definitions/email-delivery-rate). ## 2\. What influences deliverability and reputation? ### 2.1. Spam filtering Mailbox providers, such as Google and Outlook, have spam filters to stop unwanted, unsolicited, or dangerous messages from reaching the inboxes of their users. The most common reasons for emails landing in spam can be grouped into the following five main categories: 1. Domain/mailbox technical configurations 2. Volume 3. Email address history 4. Email content 5. Data quality ### 2.2. The importance of warm up Email warm up refers to the practice of gradually increasing the number of emails being sent from a newly created domain or mailbox. ### 2.3 Industry trends & deliverability Many industries such as (but not limited to) pharmaceuticals, healthcare, fintech/finance, banking, government, and defence have strict regulations that block incoming emails from getting to the end user. ### 2.4 How email providers detect patterns & associate domains Email providers like Google and Microsoft use advanced machine learning and AI to detect spammy behavior. ### The “snowball effect” of a bad reputation If enough of your secondary domains get flagged, this can trigger a snowball effect: **Stage 1: A few secondary domains start landing in spam** - Low open rates, high bounces, and complaints cause their reputation to drop. **Stage 2: Email providers recognize the pattern** - They notice new domains behaving just like the old ones. **Stage 3: Damage spreads to the main domain** ## 3\. Understanding email providers & IP infrastructure For the best deliverability, **Gmail (Google Workspace)** and **Outlook (Microsoft Office 365)** are preferred options. ### 3.1. The difference between ESPs and SMTP providers - **ESPs (Email Service Providers):** These platforms manage email services and include built-in deliverability and security features. - **SMTP Providers:** Focus on sending bulk emails, but they often carry more deliverability risks. ### 4\. Amplemarket & email deliverability Amplemarket offers a range of reporting and services to help users navigate, understand, and optimize their email deliverability. ### 4.1. Domain Health Center The Domain Health Center allows users to analyze the health stage of each of their individual mailboxes. ### 4.2. Amplemarket lead status #### Hard bounced **Leads are classified as “Hard bounced” in Amplemarket when the email does not make it to the end user because we have the incorrect email information for this lead.** ### 4.3. Amplemarket email Deliverability Booster The Deliverability Booster is Amplemarket’s mailbox warmup service that helps you build, protect and optimize your email deliverability. ### 5\. Best practices to optimize deliverability The most crucial thing when it comes to optimizing your email deliverability is to protect your domain and mailbox reputation. ### 5.1. Set up your subdomains To recap, subdomains allow you to build a sender reputation independently from your primary domain. ### 5.2. Set up the right technical configuration ### a) Authentication Ensure email domain and mailboxes are properly authenticated for in terms of Sender Policy Framework (SPF), Domainkeys Identified Mail (DKIM), and Domain-based Message Authentication. ### 6\. Deliverability troubleshooting ### 6.1. Discovery Once you understand the factors that affect your deliverability, you can kickstart your email troubleshooting. ### 7\. Conclusion Email deliverability remains one of the biggest and most overlooked issues in outbound sales. Throughout this playbook, we’ve explored email reputation in depth and shown how critical it is to deliverability success. By implementing the right strategies and committing to continuous improvement, sales teams can significantly enhance their success rates.