The Ultimate Guide for Improving Your Email Deliverability

Poor deliverability and spam folder nightmares are every email marketer’s worst fear. One week, your open rates look great, and the next, half your audience vanishes into the spam abyss. The truth is, once deliverability issues start, fixing them can take time because your sender reputation is shaped by every aspect of your email strategy.

But don’t panic. This guide walks you through a proven deliverability recovery plan, complete with a real-world success story of how one company lifted its open rate from 3% to 55% in just six months after  dealing with spam issues. 

Metrics for Identifying Deliverability

Deliverability issues can sneak up on even the most experienced marketers. So how do you identify deliverability issues? The first clue is often in your engagement metrics.

Real-world example: After a large quarterly campaign, we noticed a sharp drop in performance. A send that normally had open rates around 45% suddenly dropped to 20%. We drilled into the data by email address domain and noticed that Gmail (which made up half the audience) was the culprit. A test send confirmed the problem – the emails were wrongfully going to spam.

Side note, we all know open rates are not an accurate representation of how many people are opening the email, but they still have a place in email reporting for benchmarking sends. They were critical for helping us catch this deliverability issue!  

And so, our deliverability journey had begun. We started deliverability remediation in October 2024, and over the course of the next seven months, we closely monitored metrics like: 

• Open rates
• Click rates
• Unsubscribe rates
• Spam complaint rate (from within Marketing Cloud Engagement and Google Postmaster – more on this later)

By comparing performance for all sends, then drilling down by domain, it was clear our issue was Gmail-specific. If you notice a similar pattern, start there.

A Brief Clarification

• Email delivery is the technical look at whether your email was received by your recipient’s email server. This is best tracked by monitoring bounces.
• Email deliverability is what happens once the email is delivered, whether it’s going to the inbox, spam, or promotions folder. This is best tracked by monitoring engagement metrics and sending your own test emails.

Real-world example: Despite the changes in open rate, the bounce rate remained above 99%. Just because you have great delivery doesn’t mean you have great deliverability.

Deliverability Remediation 

Deliverability is determined by your sending domain’s setup, email authentication, and your email reputation. There is no size-fits-all approach to fixing your deliverability, so it’s important to build these things into your overall email marketing strategy. And if you find yourself with deliverability issues, here are some actionable steps you can take. 

Authentication & Bulk Sending Requirements

In February 2024, Gmail released bulk sender guidelines for senders that send more than 5,000 messages per day to Gmail accounts. Around the same time, Yahoo made a similar announcement, and Microsoft followed suit in May of this year. The most important part of these changes includes:

• Implementing SPF & DKIM
• Publishing a DMARC policy
• Keep your spam complaints below 0.1% and never go above 0.3%
• Implement a list-unsubscribe header which supports one-click unsubscribe

The first step in your deliverability journey should be to check that these technical requirements are in place and working. A Google Postmaster account will confirm your authentication and show your spam complaint rate by day over the last 120 days. Email tools like Salesforce Marketing Cloud Engagement will automatically add the one-click list unsubscribe to your header. To confirm this, send a test email to your Gmail address, view the header code, and search for “list-unsubscribe.”

An important note about Gmail spam complaints: Gmail does not share individual complaint data or use traditional feedback loops that send data back to email service providers. This means complaint rates in your email tool don’t include Gmail, which is why setting up a free Postmaster account is important!

IP Addresses & Blocklists

The other technical thing to check is your sending IP address. When it comes to emails, you are using one of the following:

• Shared IP – Used by multiple senders from your email service provider for low-volume sending. The reputation of others using the IP address impacts your sends.
• Dedicated IP address – Exclusively used by one sender that maintains and controls the sending reputation. This requires a consistent sending strategy at higher send volumes.

If you have deliverability issues, contact your email service provider support team, as they may be able to provide backend information. This is especially true if you are using a shared IP address, because it could mean another sender is hurting the IP reputation.

If you’re on a dedicated IP, you are responsible for maintaining the reputation. The first thing to check is whether your IP is on any blocklists. A tool like MX Toolbox can help with this. The other thing to check is your monthly send volume from that IP address. Salesforce recommends a minimum of 100,000 emails per month for a dedicated IP address up to a maximum of two million emails per day. It’s important to consistently meet this minimum threshold to keep your IP warm, otherwise you may start having reputation issues which can cause emails to go to spam.

Submit a Bulk Sender Form (for Gmail)

If you’ve made it through all these checks and are seeing issues in Gmail specifically, it’s time to submit a bulk sender form request for mitigation. Submitting this form allows you to outline your issue. Google will then temporarily disable some of their signals responsible for spam classification with the goal that once they put the signals back in place, you should be able to send without issues.

You can submit this form every two weeks through the duration of your deliverability issues, but it will only help if you meet all the bulk sender requirements already. 

Review Your Campaigns

Deliverability isn’t just technical—it’s strategic. Poor content or data practices can hurt your reputation, too.

Content

While there is no exact list of words that will cause your email to go to spam, the words you choose matter. Words like “free,” “urgent,” and other time-sensitive or promotional words are common spammy words that may raise a red flag in providers like Gmail. If you’re using these words, can you reduce or remove them from your campaigns? You should also try to limit the amount of links in your email that go to a domain other than your own. And finally, make sure that your emails have an easy way to unsubscribe (and that your unsubscribe process is actually working!). Don’t try to hide your unsubscribe link – it’s much better for someone to unsubscribe than to mark you as spam! 

Test tip:

1. Take one of your emails and copy it two times. 
2. Remove content from your emails as follows:
   1. In email 1, leave only text.
   2. In email 2, leave only images. 
   3. In email 3, leave only links and buttons.
3. Send a test of each email, and see where the emails get delivered. For example, if the image version goes to your inbox, but the text version goes to spam, try changing your content and test again.

Data

Now it’s time to look at your data. Ask questions like:

• Where are you getting your data from?
• Are your recipients opting in to receive emails from you?
• Are you sending the content that they signed up for? 
• When was the last time you cleaned your list? Think things like removing bad email addresses, unengaged contacts, duplicates, etc.
• How many emails are you sending per month?
• Is your sending quantity consistent? 

Back to our example, this is where we started to see some issues. When looking at the send quantity by month, we noticed that there was a huge variation in send quantity month over month. In 2024, one month’s send volume was as low as 200,000, and in another month, it was over 2.1 million. Spam algorithms want you to be predictable and reliable as a sender, and this much variance was a red flag. We spent some time with our email send strategy and determined that we could spread out our largest campaign evenly over three months rather than doing the sending all in one week.

IP and Domain Re-warming

Once content and data is cleaned up, it might be helpful to “start fresh.” 

Start with an Internal Send

The first goal is to show email service providers that people want to receive your emails. The next time you kick off a campaign, consider starting internally. Gather personal email addresses of colleagues and friends, and send the email to this list. Ask them to mark the email as “Not Spam” if the email shows up in their spam or junk folder, then have them open and click a link in the email. Start with 30-60 email addresses and repeat this process if needed. 

Warming Process

Depending on the severity of the issue, another option to consider would be to act like you are warming a brand new IP address. This process involves sending to a small subset of the most engaged subscribers first, then gradually increasing the number of sends each day. This process can be slow and tedious, but that’s why it helps build credibility – spammers aren’t willing to do it!

Get Rid of Unengaged Contacts

It’s tempting to hang on to everyone in your list because of the fear that smaller lists = fewer conversions, but that’s not usually the case. If people aren’t engaging with the emails, they probably aren’t interested anymore, and continuing to send to them can hurt your send reputation. 

In our example, we noticed a high percentage of contacts that hadn’t engaged in the last six months. We introduced a tiered engagement structure in our sends. 

• Start by sending to subscribers that were active in the last 90 days
• If spam complaints stayed under 0.1% for three weeks, extend to engaged subscribers in the last 120 days. 
• Repeat the same monitoring, then extend to 150 days, and so on. 
• Don’t send to anyone who has received at least 3 emails and not engaged in the last 9 months.

The right engagement limits will vary by business, but we believe that this was one of the most important changes to fixing the deliverability issues in our example. We started this process of excluding unengaged contacts in March 2025, and by June, our open metrics were comparable to the same time the previous year. 

Make Deliverability Part of Your Ongoing Strategy

Deliverability isn’t a one-time fix—it’s a long-term habit. As you’re thinking about your overall email marketing strategy, consider these things:

• Instead of completely removing unengaged contacts, give them one more chance to engage. Create a re-engagement journey for people who haven’t been engaging with emails. Permanently unsubscribe or remove contacts that don’t respond.
• Make sure your contacts are opted in to receive emails. Consider adding a double opt-in strategy if you don’t already have one, to ensure you’re only sending to people who want to hear from you. This is a legal requirement in some countries anyway.
• Remove or suppress people who haven’t engaged in X months or years (whatever makes sense for your business).
• Review your content to make sure it’s engaging AND what the subscriber signed up to receive.
• Prompt subscribers to add your sending address to their contacts/address book.

The bottom line:

Deliverability recovery takes time, patience, and consistency—but it’s absolutely achievable. By focusing on technical setup, content quality, engagement, and data hygiene, you can rebuild trust with inbox providers and regain strong performance.

If you find yourself in a similar situation, take a deep breath, grab a coffee, and start working through these steps. And if you ever need an expert eye on your setup, reach out! We’re happy to help you get your emails back where they belong: in the inbox.