Email deliverability best practices: Your guide to success in the inbox

You've crafted the perfect cold email. Compelling subject line, spot-on personalization, messaging that hits just right. 

You hit send, check your stats a few days later, and... nothing. 

Zero opens, zero replies.

Here's the problem: your email probably never made it to their inbox in the first place.

The best email in the world is worthless if it doesn't get delivered. And right now, it's harder than ever to get past spam filters and email gatekeepers. But the strategies below will help you build a reliable email program that actually reaches your prospects.

Let's dive in.

Generic emails kill your deliverability; focus on relevance

The foundation of good deliverability starts with relevance, but not for the reason you might think. 

Sure, relevant content gets better responses. But it also sends powerful signals to email service providers (ESPs) about whether your messages are wanted or unwanted. (Read: “spammy.”)

When people consistently ignore, delete, or mark your emails as spam, ESPs take notice. They start treating all your messages as suspicious. But when recipients open your emails, read them, and actually reply? That tells ESPs your messages have value.

Here's how to make your emails relevant enough to boost deliverability:

• Segment your lists based on industry, role, company size, or other meaningful criteria
• Craft targeted messaging that speaks directly to each segment's specific challenges and needs
• Personalize subject lines and openings with specific references to their company or role
• Reference recent company news or achievements to show you've done your homework

Remember, engagement drives deliverability. It's not enough to just avoid the spam folder: you need people to actually want your emails. 

When they do, everything else gets easier.

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Choose an ESP that won't let you down

Think of your ESP as your deliverability partner, not just an email-sending tool. The platform you choose has a direct impact on whether your messages reach inboxes or get filtered out before anyone even sees them.

Here's the reality (and you’ve likely already realized this yourself): not all ESPs are created equal when it comes to deliverability. 

Some have spent years building relationships with Gmail, Outlook, and other major ESPs. Others? Well, let's just say they're better known for the spam that comes from their servers.

Here are some things to look for in a quality ESP:

• Strong reputation and infrastructure with dedicated deliverability teams
• Authentication setup assistance for SPF, DKIM, and DMARC records
• IP warm-up processes and guidance for new sending domains
• Detailed delivery reporting so you can track performance
• Transparent sending practices and good relationships with major ESPs

Avoid bargain-basement solutions or platforms known for being used by spammers; guilt by association is real in the email world.

Your ESP should also provide transparency about their sending practices and maintain good relationships with other major players like Gmail, Outlook, and Yahoo.

Set up secondary domains to protect your reputation

Here's a scenario that plays out every day: a seller starts cold emailing from their main company domain, runs into deliverability issues, and suddenly the entire sales team's emails start getting blocked. 

Don't let this be you.

When deliverability problems arise — and they will — you want them contained to your outreach efforts and NOT affecting your entire organization's email reputation.

Typically, I approach this by setting up a secondary domain or subdomain specifically for outreach campaigns. 

For example, if your main domain is company.com, you might use outreach.company.com or mail.company.com for prospecting emails. This creates a buffer that protects your primary domain's reputation while still maintaining brand consistency.

Make sure your secondary domain is properly authenticated and gradually build its reputation through the warm-up process we'll discuss next.

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Warm up new mailboxes the right way

Think of mailbox warm-up like building trust with someone you've never met. 

You wouldn't walk up to a stranger and immediately ask for a huge favor, right? Same principle applies to ESPs.

When you start sending from a new email address, ESPs don't know if you're legitimate or just another spammer. They need to see proof that real people want your emails.

Here's a warm-up approach that’s served me well:

• Week 1: Start with 5-10 emails per day per mailbox
• Week 2: Increase to 10-20 emails per day
• Week 3: Scale to 20-30 emails per day
• Week 4+: Reach your target volume, preferably staying below 50 emails per day (never exceeding 80 emails per day)

The key is engagement-driven warm-up. Don't just send emails: make sure some of them get opened and replied to. Reach out to colleagues, partners, or warm contacts who will naturally engage with your messages. 

This positive engagement signals to ESPs that your mailbox sends valuable content.

Ditch the tracking pixels. (Seriously)

We get it: tracking can be essential. How else do you know if someone opened your email? But here's the uncomfortable truth: tracking opens might be doing more harm than good.

Those invisible tracking pixels that tell you when someone "opened" your email? Spam filters hate them, especially when they come from domains that don't match your sender address. Plus, the data you're getting often isn't even accurate.

Think about it: many email clients now block images by default, and some automatically "open" emails without the recipient actually reading them. The data you get often isn't reliable enough to base real decisions on.

Our recommendation: disable open rate tracking unless you specifically need it for troubleshooting deliverability issues. If you must use this feature, make sure the domain matches your sending domain.

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Track what actually moves the needle

Now, while we do recommend limiting pixel use, we absolutely also recommend measuring your email performance. Because here’s the thing about deliverability: problems don't just announce themselves. Your delivery rates can be silently declining for weeks before you notice. A sudden drop in delivery rates or spike in bounces could signal a reputation issue that needs immediate attention.

That's why consistent performance monitoring isn't optional: it's essential.

But you also don’t have to monitor EVERYTHING; there’s no need to boil the ocean here. What you should do is identify — and focus on — the right metrics that will actually help you improve deliverability; it’ll also help if you identify the metrics that are just noise that you can ignore. 

Here are the metrics we recommend focusing on:

• Delivery rate: What percentage of emails actually get delivered
• Reply rates: Your ultimate success metric
• Bounce rates: Including specific error codes to understand why emails bounced
• Unsubscribe rates: Higher rates may indicate relevance issues
• Spam complaint rates: Critical for maintaining sender reputation
• Open rates: Useful for troubleshooting, but not always reliable

And here are the ones we consider to be “vanity” metrics that you can ignore – or, at the very least, give less weight to:

• Click-through rates: Nice to know, but doesn't impact your sender reputation.
• Forward rates: Rarely accurate and not a deliverability factor.
• Social shares: Completely irrelevant to whether your emails reach inboxes.

Set up regular reporting so you can spot trends before they become serious problems. Trust us, it's much easier to fix a small deliverability issue than recover from a major reputation hit.

Monitor your reputation behind the scenes

Your performance metrics show you the results, but they don't tell you what's actually happening behind the scenes. ESPs are constantly evaluating your reputation as a sender, and most of that evaluation is invisible to you.

Here's the problem: you might think everything's fine because your emails are getting delivered, but your reputation could be slowly declining. By the time you notice delivery issues, it's often too late.

That's why you need visibility into how ESPs actually view your sending practices.

Here are some key ways to monitor your reputation:

• Inbox placement testing to see where your emails actually land
• Blocklist monitoring to catch any reputation issues early
• Authentication verification ensuring SPF, DKIM, and DMARC are working
• Reputation checks across major ESPs
• Proactive alerting for sudden changes in bounce or spam complaint rates

Consider setting up proactive alerts for potential issues like sudden increases in bounce rates or spam complaints. The sooner you catch problems, the easier they are to fix. Nobody wants to discover their domain has been blocklisted after running a major outreach campaign.

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Don't blast all your emails at once

Picture this: you wake up Monday morning, chug your coffee, and decide to power through your weekly outreach by sending 300 emails between 9 and 10 AM. 

Then, you go dark for three days, only to blast another 200 emails on Friday afternoon before heading out for the weekend.

To ESPs, this doesn't look like a human reaching out to prospects: it looks like a bot following a script.

ESPs have gotten really good at spotting unnatural sending patterns. They're looking for signs that suggest mass automation rather than thoughtful, personalized outreach. And when they spot those patterns, they start treating your emails with suspicion.

Here's how to send like a real person would:

• Limit daily volume to under 50 emails per mailbox
• Spread sending throughout the day rather than sending everything at once; focus on establishing a smooth cadence and avoiding spikes
• Maintain consistent patterns across days and weeks; again, goal here is to avoid spikes
• Limit follow-ups to unresponsive recipients to three emails; then, switch to other channels like LinkedIn and calls
• Remove unresponsive contacts after multiple failed attempts

When it comes to follow-ups, here's some tough love we all need to hear: if someone hasn't responded after three emails, they're probably not going to. Continuing to email them only hurts your sender reputation and wastes time you could spend on better, more qualified prospects.

Scale up without screwing up

Your outreach program is finally hitting its stride. Replies are coming in, meetings are getting booked, and your manager is asking if you can double your volume next quarter. The temptation is real: just crank up the dial on your existing setup and watch the leads roll in.

But here's where most sellers make a costly mistake. 

They try to squeeze more emails out of the same mailboxes instead of properly expanding their infrastructure. It's like trying to serve a packed restaurant with just one cook: sure, you might pull it off for a night, but you're setting yourself up for disaster long term.

ESPs notice when a mailbox that normally sends 50 emails a day suddenly jumps to 200. That kind of volume spike screams "something changed," and not in a good way.

Here are some recommendations for how to scale the smart way:

• Add domains and senders as volume needs increase, rather than overloading existing ones
• Automatically rotate IPs to distribute sending across multiple addresses
• Stagger warm-up periods so new infrastructure comes online gradually
• Plan several weeks ahead for any capacity increases

Remember, successful scaling takes patience. You can't just flip a switch and double your email capacity overnight; plan for several weeks of preparation when adding new sending infrastructure.

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Get smart about advanced sending features

You've nailed the basics. Your emails are getting delivered, your warm-up process is solid, and you're seeing consistent results. Now you're wondering: what's next? How do the pros squeeze even better performance out of their email programs?

This is where intelligent email sending comes in. Advanced email systems can make smart decisions about every message — like which mailbox to send from, when to send it, and even which prospects are most likely to respond. It's like having a really smart assistant who knows all the deliverability tricks.

But here's the thing: not every team needs to go this deep. If you're sending a few dozen emails a week, stick with the fundamentals. But if you're running larger campaigns and want to optimize every detail, these features can make a real difference.

Here are some key tactics for executing intelligent email sends:

• Inbox rotation between multiple sending addresses
• ESP matching to align your sender with the recipient's ESP
• Prioritize recipients who are more likely to be responsive

While not every organization needs this level of sophistication, these features can significantly improve results for teams running larger campaigns.

Take data hygiene seriously. (Your reputation depends on it)

You've spent hours crafting the perfect email sequence. Your subject lines are dialed in, your messaging hits all the right pain points, and you're confident this campaign is going to crush it. 

Then, you upload your prospect list and hit send … without realizing half the email addresses are outdated, misspelled, or just plain fake.

Here's what happens next: your bounce rate spikes, spam complaints roll in, and ESPs start viewing you as sloppy at best, spammy at worst. 

All that careful work on your messaging? Completely wasted because of poor data hygiene.

Most sellers don't realize that list hygiene is just as important as email copy. ESPs are constantly judging you based on who you're trying to reach and how they respond. Send to enough bad addresses or unengaged contacts, and you'll find yourself in deliverability jail.

Here are some key ways to maintain clean data:

• Verify email addresses before sending to catch typos and inactive domains
• Remove hard bounces immediately after campaigns
• Clean out consistently unengaged contacts after multiple attempts
• Avoid role-based emails like info@company.com or sales@company.com
• Regularly audit your lists to maintain high-quality prospect data

Clean data doesn't just improve deliverability: it improves everything. Better engagement rates, more meaningful conversations, and higher-quality leads. It's a win across the board.

The bottom line

Look, email deliverability isn't the most exciting part of sales, but it's absolutely critical. All the clever copywriting and perfect timing in the world won't matter if your emails never reach their intended recipients.

The good news? You don't need to become a technical expert to see real improvements. Start with the fundamentals: relevant content, proper infrastructure, and gradual warm-up processes. Then, build from there with monitoring, optimization, and smart sending practices.

Most importantly, remember that deliverability is an ongoing process, not a one-time setup. ESPs are constantly updating their algorithms, and what works today might need adjustment tomorrow. Stay curious, keep testing, and always pay attention to what your data is telling you.

Your prospects are out there waiting to hear from you. Now, you know how to make sure your emails actually reach them.