The Ultimate Email Deliverability Guide for Sales Outreach 

The Ultimate Email Deliverability Guide for Sales Outreach 

Email service giants like Gmail, Yahoo, and Outlook have done an excellent job over the years protecting their users from harmful and irrelevant emails, keeping their inboxes clean and secure. 

The only downfall is that these increasingly rigorous securities are not perfect, and they can sometimes flag legitimate, potentially useful emails, creating challenges for businesses trying to connect with potential customers. 

No matter how relevant, interesting, and personalized a sales or marketing email is — it won’t matter if it doesn’t reach the recipient’s inbox in the first place. This is where email deliverability steps in. 

Stick around for this compact, all-in-one guide covering the key aspects of email deliverability to ensure your emails land in their designated inboxes, paving the way for countless business opportunities.

What is email deliverability? 

In a nutshell, email deliverability is the ability to ensure that emails are delivered to the recipients in their inbox folders. 

Not to be confused with email delivery, which is a more general term that refers to emails getting ‘past’ mail servers like Gmail, without focusing on which folder they may end up in, including spam. 

Email deliverability takes it a step further by focusing exclusively on the primary inbox folder — the one always checked by users. This provides a much more accurate picture of one’s email outreach performance because while their delivery rate could be 100%, if all the emails are landing in spam (or promotion, social) folders, they will never get opened or replied to in the first place.  

How does deliverability work? 

The way deliverability works is quite complex, but in simple terms, once you hit ‘send’ — your email first goes through a special security check by the recipient’s mail server. If your email authentication, authenticity, content, and domain reputation (among other things) check out, only then will their server give passage to your email. If not, it’s instead sent to the spam folder or blocked from entering at all. 

One of the most common questions sales and marketing teams have when it comes to the topic of deliverability is ‘What is a good email deliverability rate?’. If you look around the internet, you will notice that every website has a different answer, ranging from 70% to 90% as the acceptable threshold. 

We advise to aim somewhere in the middle at around 80% as the absolute minimum, and if for some reason it’s lower — there are several proactive steps businesses should take to improve email deliverability.

Why is email deliverability important? 

Besides the most obvious significance of strong email deliverability — businesses will actually reach their potential customers with sales and marketing emails, whether it’s to promote a new product/feature or break the ice with the relevant decision-maker, there are several other reasons why it’s so important: 

  • Since more emails are delivered, more emails will be opened, read, and replied to, leading to increased conversion rates and sales with greater cost efficiency. 
  • Low deliverability email metrics damage your company’s domain in the eyes of email service providers, creating a vicious cycle of poor email performance that becomes increasingly challenging to fix. 
  • Putting effort into deliverability equates to numerous email best practices being followed — legal compliance (like GDPR), accessible opt-out, contact list hygiene, etc., all of which not only increase email deliverability but also elevate email performance and brand reputation. 

What affects email deliverability?  

Your recipients’ email providers are ultimately the judge and jury on whether your emails are allowed to reach their inbox, but there are certain factors taken into account when making that decision. 

Here are the 5 most common ones: 

1. Do your emails trigger spam traps? 

Spam traps are exactly what they sound to be — special traps in the form of fake or outdated emails that signal to email providers of probable spam-like behavior. This mostly occurs when companies buy contact lists or mass scrape from the internet.  

2. Are your recipients engaging with your emails? 

Believe it or not, ISPs and email providers take into account how well their users are engaging with your emails, because the logic is that if they aren’t — your emails are irrelevant and/or unwanted.

How often are recipients flagging your emails as spam? How about unsubscribing? Your spam rate is the most crucial metric for deliverability, even more so amid the new Google policy updates (more on that below).  

3. Are your emails properly authenticated? 

Email authentication refers to the proper setup of your email account to ensure mail providers that your emails are legitimate and safe, and that you, as the sender, are who you say you are.

The 3 core authentication standards include SPF, DKIM, and DMARC. Without these authentications, it is highly likely that your deliverability will suffer, let alone for mass outreach.    

4. Are you sending too many emails? 

Even in the context of bulk, mass-email campaigns, there are limits. A newly created email account that starts sending thousands of emails right away will most definitely get flagged.

This is why it’s crucial to always warm up your email account by gradually increasing the volume of emails sent while gradually decreasing the interval. Just for reference, as of 2024 — the limit for Gmail is 10,000 per day, with much stricter requirements starting at the 5k mark. 

5. Is your email content spam-free?  

This may be unexpected to some, but the content of an email does have the potential to affect deliverability. It’s worth mentioning, however, that if your spam rate is very low and all the above points are covered, email content will have minimal impact on deliverability.

Examples of email content that could be flagged by spam filters include numerous spam trigger words (e.g. ‘risk-free’, ‘act now’), high ‘image-to-text’ and ‘link-to-text’ ratios, etc. 


Failing to act on the above-mentioned points you risk getting on a blocklist, which is a database of email domains that are believed to be sending spam. Think of it as a purgatory for email domains which will make it very difficult to bring back to life.

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7 Email Deliverability Best Practices 

Now that we’ve outlined the biggest causes of deliverability issues, let’s dive right into how to improve email deliverability and ensure your emails safely reach their intended recipients at all times. 

Target only relevant prospects 

When crafting your email campaigns, precision targeting is key. Sending emails to relevant prospects ensures higher engagement rates, as recipients are more likely to open and respond. 

While this may seem counterintuitive, mass email outreach to non-targeted prospects increases the likelihood of them being marked as spam and you getting unsubscribed, while helping you maintain a positive sender reputation. 

With new spam rate limits of 0.1% as of 2024, focusing on relevance and fostering meaningful connections over quantity becomes even more essential for long-term deliverability success.

Warm up your email domain 

Introducing a new email domain requires a gradual email warm-up process to establish a strong sender reputation, which then has to be regularly monitored. Your sender reputation is a combined score of your domain reputation and your IP reputation, and it shows email providers how reliable, legitimate, and un-spammy your business and your email outreach is.

While IPs are often shared (unless you’re sending over 100,000 emails a month), domain reputations can and should be the responsibility of the company.

Whether manually or with a dedicated warm-up tool, sales and marketing teams must gradually manage email volume and delivery timing to demonstrate consistent relevance and engagement over time.

By earning the trust of email providers through a gradual increase in volume and reliability, businesses pave the way for scalable and effective email outreach strategies.

Establishing email authentication  

We already talked about authentication protocols as one of the main factors affecting deliverability, and once again, this is something that Google emphasized during its recent policy updates. 

While the initial setup may require technical expertise, it’s a one-time process that then only needs monitoring to ensure everything is running smoothly. 

The other good news is that while in the past it would take someone from IT to set up the key authentication protocols — SPF, DKM, DMARC, modern email outreach tools offer built-in, user-friendly solutions to implement authentication protocols seamlessly.

In Reply, for instance, we have a dedicated ‘domain health-checker’ tab that helps users set-up their authentication protocols and provides actionable suggestions on improving email deliverability. 

Comply with email regulations 

This one is pretty straightforward — companies have to ensure they are complying with the recipients’ local regulatory authorities that cover email outreach policies. 

They vary from one country to another, however, they do share some core key principles such as accessible opt-out, no spam practices, and other core transparent communication practices. 

The most common email regulations in the world include: 

– GDPR for EU   

– CAN SPAM Act for the US

– The Privacy and Electronic Communications Regulations for the UK

Companies must familiarize themselves with relevant regulations in their target regions to ensure compliance and avoid penalties or reputation damage.

Maintain contact list hygiene

Keeping your contact list clean and regularly updated is vital for maintaining deliverability and sender reputation. Some of the key principles of contact list hygiene include: 

  • Regularly verifying email addresses to ensure they are legitimate and actually used to avoid spam traps, keep engagement rates high, and make your outreach efforts worth the time and effort.

  • Removing contacts with bounced emails (emails that return to the sender because they failed to deliver). Hard bounces are permanently rejected emails for reasons such as an invalid email address or domain not found, and these should be removed right away. Soft bounces may be given the benefit of the doubt for a few tries because they may simply signify that the recipient’s inbox is full.

  • Remove completely unengaged contacts from your email lists to keep your engagement rates high while signaling to keep your spam and unsubscribe rates at bay.

  • Avoid purchasing email lists at all costs to preserve the integrity of your outreach efforts and foster genuine connections with recipients.

Provide accessible opt-out 

In line with recent policy updates from major email providers, including accessible opt-out options in every email is a non-negotiable practice. Recipients have to be able to unsubscribe from your emails with a simple click of a button, without looking for it for more than a second. 

Ensuring that recipients can easily unsubscribe from your email lists not only demonstrates respect for their preferences but also helps maintain a positive sender reputation. In any case, this is a great practice because why would you want uninterested contacts receiving your sales or marketing emails?

While on the topic of opt-out, it’s also highly recommended to include a double opt-in policy for marketing emails to further enhance transparency and recipient consent. However, it’s understandable that this may not be feasible for cold sales outreach where companies reach out to prospects and decision-makers without them showing explicit interest first.


The content of your emails should always be top-notch, because given that your deliverability is healthy — it will be up to the email message itself to either entice and engage the recipient or not. 

At the same time, certain aspects of email content can negatively affect deliverability, so here are some quick tips to ensure that doesn’t happen: 

– Numerous instances of poor grammar present 

– Including all-caps words and phrases, especially in subject lines 

– Including numerous spam trigger words 

– Including too many images and/or links with little text 

Crafting personalized, genuine email messages not only better resonates with recipients and avoids triggering spam filters, but also ultimately contributes to the success of your email sales and marketing efforts.


For more tips and best practices, check out our compact Email Deliverability ebook below for a step-by-step checklist that will ensure all your emails reach their destination.  

Email deliverability checklist (including proven tools)

It doesn’t matter how good your template is or how personal your emails are, if your emails are destined to the SPAM folder.

Follow this checklist to make friends with SPAM filters and ensure top deliverability for your outreach emails.

Tools to monitor and measure deliverability 

It is fair to say that deliverability is an integral part of every modern email outreach workflow, and it requires proper initial setup and constant monitoring to ensure everything is running smoothly. 

Any sudden changes in metrics affecting email deliverability and sender reputation have to be acted on swiftly to avoid any serious damage, and the best way to do this is by gearing up with the necessary deliverability software. 

We have a dedicated article on building a fully-functioning deliverability toolset for those interested, but here are the key email deliverability tools to setup, monitor, and manage every aspect of effective inbox placement: 

  • Email domain technical setup → Mail-Tester (receive a detailed report of your authentication protocols and confirm that every part of your email campaign is optimized for deliverability) 
  • Email warm-up and reputation management → MailToaster (automatically build, maintain, or repair your sender reputation to boost inbox placement) 
  • Email validation and verification → ZeroBounce (detect poor-quality email addresses that can sabotage your inbox rates, remove invalid contacts and spam traps) 
  • Spam rate monitoring → Google Postmaster (get detailed dashboards of your spam rates in real time and check email deliverability metrics of your domain and email campaign performance) 

Understanding the importance of deliverability and users’ preference of not juggling numerous tools, we’ve recently integrated Google’s Postmaster API into Reply, empowering our users to manage their spam rates and check email deliverability performance in real time right through the platform. 

Improve your email deliverability with Reply 

Taking the necessary steps to ensure flawless email deliverability may take quite some effort, but it is the foundation of successful business outreach.

And even though bulk email policies have gotten much stricter over the years, outreach software didn’t fall behind. In fact, they took significant steps by integrating new features aimed to simplify and streamline deliverability setup and monitoring. 

At Reply, we’ve added Google’s Postmaster API so our users can track their spam rates right through the platform, a dedicated health-checker to help users set up authentication protocols, and much more. Feel free to check out our new deliverability features in more detail to see them in action. 


In summary, mastering email deliverability is crucial for all businesses to ensure effective sales and marketing communication with their potential customers. By following the above-mentioned deliverability email best practices and gearing up with the right tools, businesses can optimize their email outreach efforts and achieve greater success in engaging prospects and driving conversions.

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