7 Email Deliverability Upgrades (Improving Open Rates by 30%!)

It doesn’t matter how clever your pitch is if it never reaches the inbox.

In 2025, email deliverability is a bigger challenge than ever. Strict sending requirements, more advanced spam filters, and heightened inbox protection measures mean that even legitimate emails are at greater risk of being flagged or ignored. 

Senders — and sellers — must adapt or risk being lost in the noise. We’re here to help you break through.

Over the last few months, the Apollo team made three key updates on the backend to give your emails a better chance of being seen:

• Automatic IP rotation ensures your emails are sent from reliable IPs, improving open rates by 30%
• More accurate open rates by filtering out bot opens, so you only see real engagement
• Smart send queueing prioritizes email sends to prospects based on data quality 

There are also four new steps you can take to improve your email deliverability:

• Add multiple tracking domains for more control over your sender reputation
• Double-check your domain setup with our refreshed diagnostics
• Run third-party email validation on prospects’ email addresses
• Write with Apollo's latest AI model to personalize better at scale

By combining these backend improvements with smart sender practices, you can boost your chances of landing in the inbox and getting real responses.

3 Backend updates for better opens & engagement

Here’s what’s new under the hood at Apollo, designed to improve open and engagement rates, without you having to lift a finger.

Let’s start with some background. Like any device that’s connected to the internet, servers that send out your emails have unique IP addresses. This IP collects a “reputation” based on the quality of engagement and sending behavior happening on it. 

Your IP reputation alongside your domain reputation make up your overall sender reputation — which is how mailbox providers judge whether your message should go to the inbox or get flagged as spam. So having a good IP reputation is key to maintaining good deliverability. 

However, you’re not the only sender on a particular IP (unless you’re set up to use your own dedicated IP address). Email service providers, including sales outreach tools like Apollo, send their customers’ emails from shared IPs. So the behavior of all the senders on a shared IP will impact its reputation.

Providers can rotate, or switch, between multiple IP addresses when sending emails to minimize risks, avoid spam flags and damaging hits to IP reputation.

With the latest improvements to our email infrastructure, Apollo rotates IPs constantly, can quickly isolate bad senders, as well as spin up fresh IPs quickly — so you can be sure that your emails are sending from an IP with a strong reputation.

After implementing automatic IP rotation, we’ve already seen email open rates across Apollo users improve by 30%!

“Most outreach platforms don’t filter out bot opens, which will artificially inflate reported email performance,” says Nipun Jami, Principal Product Manager at Apollo.

Here’s why that matters. 

Bots are opening and clicking on your emails right now — and that’s okay! This type of bot is deployed for good reason, like to provide better security or help you scan your inbox. It also doesn’t mean that the actual email addresses behind the opens or clicks are fake.

For example, email security solutions (from antivirus tools to corporate firewalls) will “open” emails to scan for malicious content. Some email providers or servers will confirm that links in messages are safe. Email apps will open emails to prefetch content, so you can have a better experience with preview snippets or not having to wait for images to load when you do.

That being said, these bot opens can inflate your open (and click) metrics if your sending platform doesn’t filter them out. These days, spam filtering systems look at actual recipient behavior, so it’s important to get a clearer understanding of what’s actually happening without the noise of bot activity.

Over the past few months, Apollo has started to filter out bot opens, so that reporting is more accurate. (You can also choose to include or exclude bots when creating custom analytics reports and dashboards.) 

Nipun explains, “By focusing on human interactions, the metrics truly reflect prospect interest. Now you can make more reliable data-driven decisions, and create workflows or follow-ups based on genuine engagement.”

We recommend asking your sales email providers what is — and isn’t — going into their open rate calculations. Learn more about bot tracking here.

The order in which emails send matters. We found that programmatically sorting before sending can make a big difference in engagement.

That’s why we built smart send queueing.

Until now, the order in which you added contacts determined the order emails were sent (unless manually marked as high priority). 

This “first in, first out” method may deprioritize leads with a higher likelihood of engagement, so that their emails send later — especially when considering email sending limits.

Now Apollo’s smart send queueing sends more intelligently, based on this order:

1. Scheduled or High-priority: Your own preference takes precedence. Emails that you set for a specific time or flagged as high priority go out first.
2. Verified contacts: Then, Apollo will send to contacts with verified email addresses.
3. Everyone else: Finally, any remaining emails follow the original “first in, first out” order.

This ensures leads with higher-quality data get their emails sooner and builds up positive email performance, contributing to healthy deliverability.

With this update, we’re seeing promising results, including a 25% decrease in spamblock rates, 9% decrease in overall email bounce rates, and an 8% increase in open rates.

4 new steps to land in more inboxes

Here’s how you can act on Apollo’s additional email infrastructure updates to improve deliverability and reach more prospects.

Tracking domains are used to track email engagement. Platforms usually have shared tracking domains for their customers to use out of the box. Here, too, bad actors can damage deliverability for the pool. 

Setting up custom tracking domains helps protect your reputation from the actions of other senders.

Now you can set up multiple custom tracking domains in Apollo and configure each mailbox with a specific tracking subdomain.

We recommend matching custom tracking domains to the number of sending domains you’ve set up. For example, let’s say you’re using two different sending domains, and you have four mailboxes set up:

• user1@hellodomain.org
• user2@hellodomain.org
• user1@trydomain.org
• user2@trydomain.org

You’d connect the first two mailboxes to a tracking domain like clicks.hellodomain.org and the last two mailboxes to a tracking domain like clicks.trydomain.org.

Learn more about custom tracking subdomains and how to reconfigure any existing mailboxes you’ve linked to Apollo.

Proper setup of your sending domains is table stakes for good deliverability. 

Apollo’s domain setup checks are now more robust — leading to improved issue detection, more accurate diagnoses of authentication status, and more information to troubleshoot.

Double-check your domain authentication statuses for the latest, most accurate picture of your setup.

This is highly recommended! This update resulted in some records now appearing unhealthy or pending (though they may previously been marked healthy).

To review your domain authentication:

• (Per mailbox) Go to a linked mailbox and click through to “Check mailbox health”
• (Across your sending domains) Click the “Run diagnostics” button at the top of the Sequences page.

Apollo already has a built-in email verification process with a 91% accuracy rate, and you can use the email status filter in a People search to make sure you’re getting verified, safe-to-send email addresses.

If you’re interested in an extra layer of email verification, run by a third-party validation tool, Apollo’s new Waterfall Enrichment tool makes this possible! 

Waterfall Enrichment allows you to check multiple data sources (in addition to Apollo) for an email address and then add an email validation step using tools like ZeroBounce. 

Apollo Waterfall Enrichment is currently in beta. You can sign up here to join the waitlist.

When it comes to the email message itself, relevance is the best way to avoid the spam folder. But personalizing all your messages can be time-consuming to do at scale. 

Use Apollo’s AI Power-ups to generate unique, relevant emails. 

You can create a custom power-up using Apollo’s AI copywriter — which now leverages the latest AI model from Anthropic, Claude 3.5 Haiku.

Or start with one of our many AI Power-up Templates to do things like:

• create a personalized email based on open job postings at the company

• generate an opening line from the prospect’s LinkedIn posts

• or generate a totally personalized email based on the prospect’s work context

Be sure to configure your AI Content Center first so that your research and messaging results are tailored to your company goals.

Not ready to dive in yet? Watch this lesson about using AI Power-Ups to Generate Personalized Emails. 

Keep learning

Email deliverability is not an easy topic to understand, but we have many resources to help you brush up on the basics and learn best practices to keep your messages getting into inboxes.

• Watch our webinar on how to avoid the spam filter 

• Read the Email Deliverability chapter of Apollo’s Outbound Sales book (also available on Amazon)

• Review our Email Deliverability Best Practices

• Stay up to date on what's new with deliverability and more in Apollo with our monthly release notes.

If you've got an Apollo account, you've already got access to all of these updates to our email outreach tools. And if you don’t, you can get started today for free.