The Key to Stopping Email Bounces

Kristen Wyatt on March 21, 2025

It’s no secret that email marketing is one of the most powerful tools to connect with your audience, build brand loyalty, and drive sales. But let’s be honest – nothing stings more than spending hours crafting the perfect email, hitting “send,” and later discovering it never reached your subscriber. This is where email bounces come into the picture. Bounces are a major factor in email deliverability. Understanding them can mean the difference between a successful campaign and one that falls flat. In this blog, we’ll explore what email bounces are, why they happen, and how you can effectively manage them to maintain a healthy sending list and improve your deliverability rates.

So – Why do bounces occur? An email bounce (or “bounce”) takes place when your email fails to reach the intended recipient’s inbox. Instead of landing in the inbox, it “bounces” back to you. Think of it as the digital version of a “return to sender” notice on a physical letter. Understanding where bounces come from is key to diagnosing and fixing deliverability issues. Bounces can stem from a variety of sources, ranging from technical problems to user behavior.

Let’s break them down into more detail:

1. Invalid or Nonexistent Email Addresses

One of the most common sources of hard bounces is sending email to addresses that don’t exist. This can happen for several reasons:

  • Typos during sign-up: A subscriber might accidentally type something like “gmaul.com” instead of “gmail.com.”
  • Deactivated accounts: The recipient might have deleted or abandoned their email account.
  • Disposable email addresses: Some users sign up with temporary addresses to access gated content, but these often expire quickly.

Consider using a double opt-in process during sign-up to tackle invalid or mistyped email addresses. This requires users to confirm their email by clicking a verification link. You can also use an email verification tool to catch typos or invalid formats before they’re added to your list. These steps will help keep your list clean and improve deliverability.

2. Domain-Related Issues

The domain (the part of the email address after the “@” symbol) can also cause bounces. Common domain-related problems include:

  • Nonexistent domains: The domain might not exist (example: user@nonexistentdomain.com).
  • Misconfigured DNS settings: The domain’s DNS records might not be set up correctly to receive email.
  • Expired domains: The domain may have expired or been deactivated.

Start by verifying domains during sign-up using an email validation tool. This ensures only legitimate, active domains make it onto your list. Regularly audit your list to remove domains that no longer exist. These steps will help keep your list healthy and reduce bounce rates.

3. Full Mailboxes

A soft bounce often happens when the recipient’s mailbox is full and can’t accept new mail. This is common with free email services like Yahoo or AOL which have storage limits.

In cases where an email cannot be delivered due to a recipient’s inbox being full, there’s little you can do immediately except wait and attempt to resend the email at a later time. If the issue persists, it’s best to remove the address from your list to keep it clean and avoid wasting resources. This approach helps to make sure your email list remains focused on active and reachable recipients.

4. Server Issues

Technical problems on the recipient’s side can also cause bounces. These include:

  • Server downtime: The recipient’s email server might be temporarily offline or undergoing maintenance.
  • Overloaded servers: High traffic or resource limitations can prevent the server from accepting new email.
  • Greylisting: Some servers temporarily reject mail from unknown senders as a spam prevention measure, but they usually accept the email on a later attempt.

For temporary issues, try resending the email after a few hours or days. Most email platforms automatically retry delivery over a set period. If the problem continues, remove the address from your list to maintain list hygiene.

5. Email Size and Content Issues

The size and content of your email can also trigger bounces. Some of the most common reasons include:

  • Large attachments: Campaigns with large attachments (over 10MB) may exceed the recipient’s server limits.
  • Spammy content: Certain keywords, excessive use of images, or poorly formatted HTML can trigger spam filters, causing the email to bounce.
  • Authentication failures: If your email lacks proper authentication (SPF, DKIM, DMARC), it may be rejected by the recipient’s server.

Start by compressing large attachments or replacing them with cloud storage links to reduce the likelihood of your email being flagged or blocked. Steer clear of spam-triggering words and phrases like “free,” “act now,” or “limited time offer,” as these can increase the chances of your content being marked as spam. Finally, confirm that your mail is properly authenticated (using protocols like SPF, DKIM, and DMARC) to verify your domain and enhance trust with email providers. These steps will help your email reach recipients’ inboxes more effectively.

6. Blocked Email

Sometimes, your mail is blocked by the recipient’s server or email provider. This can happen for several reasons:

  • IP/Domain blacklisting: If your sending IP address or domain is on a blacklist, your mail may be blocked.
  • Strict spam filters: Some organizations or email providers have aggressive spam filters that block email from unknown senders.
  • Recipient settings: The recipient may have manually blocked your email address or domain.

To resolve these issues, begin by checking if your IP or domain is listed on a blacklist using tools like MX Toolbox. If you are listed, follow the necessary delisting steps to request more information and address the underlying cause. If you’re sending email from a new domain or server, make sure to warm up your IP address gradually by increasing email volume over time to build a positive sender reputation. And encourage your subscribers to add your address to their contacts or whitelist. This can help confirm your mail consistently lands in their inboxes rather than spam folders. These proactive measures will improve your email deliverability and sender credibility.

7. Inactive or Abandoned Accounts

Over time, people stop using certain email accounts. But they may remain on your list. These accounts can lead to bounces if the provider deactivates them.

It’s important to regularly clean your lists by removing inactive subscribers who no longer engage with your email. Before taking this step, consider sending re-engagement campaigns to inactive users to give them an opportunity to reconnect with your content. If they still don’t respond, it’s best to remove them from your list. This practice improves your email engagement rates and helps to make sure your list remains focused on active and interested recipients that can positively impact your sender reputation and deliverability.

8. Role-Based Email Addresses

Role-based email addresses (for example: “info@company.com,” “support@company.com”) are often monitored by multiple people or automated systems. These addresses are more likely to bounce because:

  • They may not accept email from external senders.
  • They might have stricter spam filters.
  • They could be set up to automatically delete or reject certain types of mail.

Avoid sending marketing campaigns to role-based addresses, such as info@ or support@, unless you’re confident they are relevant and appropriate for your campaign. These addresses are often monitored by multiple people or automated systems. This makes them less likely to engage with your content. Instead, focus on targeting personal email addresses. These contacts tend to yield better engagement rates and provide more meaningful connections with your audience.

9. Seasonal or Temporary Issues

Sometimes, bounces are caused by temporary factors, such as:

  • Holiday auto-replies: Some email servers are configured to reject mail when the recipient is on vacation or has set up an auto-reply.
  • Temporary server rules: During high-traffic periods (for example, BFCM), some servers may temporarily tighten their spam filters.

If an email fails to deliver due to these issues (like having a recipient’s server being overloaded), try resending after a few days once the problem has had a chance to resolve itself.  It’s also important to monitor your bounce rates, especially during peak seasons when email servers often experience higher volumes. If you notice an increase in these bounces, consider adjusting your sending frequency or timing to reduce the strain on servers and improve deliverability.

To minimize bounces and enhance your marketing success, it’s incredibly important to take proactive steps that address the root causes. Start by using a reliable Email Service Provider (ESP) to automatically manage bounce-related issues, like retrying soft bounces and removing hard bounce addresses. Regularly monitor your sender reputation with tools like Google Postmaster or SNDS to catch and resolve potential issues early. Educate your subscribers to update their email addresses if they switch providers, helping your list to stay current. And don’t forget to test your campaigns before sending to check for size, formatting, and spam triggers. By understanding the causes of bounce issues and addressing them proactively, you can improve your email deliverability, reduce bounce rates, and position yourself so that your messages reach the right audience. Remember, a clean and well-maintained email list is the foundation of successful email marketing. So don’t skip the maintenance!

How To Land Into Gmail’s Inbox

Kristen Wyatt on July 31, 2023

Landing in Gmail’s primary inbox can be pivotal for email marketers and anyone sending important emails. Gmail’s inbox sorting algorithm automatically categorizes incoming emails into different tabs: 

  • Primary: Personal emails and messages from other categories where the tab isn’t turned on.
  • Social: Notifications and updates from social platforms.
  • Promotions: Promotional mail and other offers from email marketing and similar campaigns.
  • Updates: Transactional emails such as receipts and shipping notifications.
  • Forums: Mailing lists and groups.

To increase the likelihood of your emails landing in the Primary tab, follow these best practices:

Use a recognizable “From” name: Ensure your sender name is clear and recognizable. This helps recipients know who you are and why they are receiving your mail. Avoid using spammy or misleading names.

Use sub-domains: Create subdomains for each type of mail that you send (marketing, updates, transactional mail, etc). This will keep your top domain’s reputation safe. It also allows you a more detailed view of open/click tracking.  

Authenticate your domain: Implement Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting, and Conformance (DMARC) protocols to improve your email’s credibility and reduce the chances of being marked as spam.

Use a reputable email service provider: Use a reliable and well-known email service provider that actively manages its reputation to ensure high deliverability rates.

Send relevant and engaging content: Create valuable, personalized, and engaging content that recipients are more likely to interact with. Avoid using spammy language or excessive promotional material.

Avoid spam trigger words: Refrain from using common spam trigger words in your subject linked and email content, such as 

  • Free 
  • Discount
  • Limited time
  • Satisfaction guaranteed
  • No obligation 

Limit the use of attachments and large images: Emails with large attachments or image-heavy content might be considered suspicious and end up in the Promotions tab.

Avoid excessive use of links: Too many links inside your email can make it look spammy. Use links sparingly and make sure they point to reputable websites.

Maintain a clean email list: Regularly clean your email list to remove inactive or unengaged subscribers. Sending emails to unresponsive addresses may increase the chances of your emails being marked as spam.

Encourage recipients to move your emails: Include a call-to-action in your emails, asking recipients to move your emails to the Primary tab if they find them there. For example, ask them to drag and drop your email from the Promotions tab to the Primary tab.

Request adding your email address to contacts: Encourage subscribers to add your sending address to their contacts list. This action signals Gmail that the user considers your email as important.

Monitor and adjust your email strategy: Pay attention to your email open rates, click-through rates, and spam reports. Consider utilizing Google Postmaster Tools to gain more detailed insight into how Google views your sending domain(s). Adjust your email strategy based on the data to improve engagement and reduce spam complaints.

Remember, getting into the Primary inbox is not entirely within your control. Gmail’s algorithms are dynamic and always subject to updates. However, following these best practices should help improve your chances of landing there. Also, make sure that you comply with Gmail’s guidelines and policies to maintain a positive sender reputation.

IP Warming: What You Need To Know

Kristen Wyatt on July 7, 2023

IP Warming is the process of systematically adding email volume to a new IP address at a gradual pace in order to establish a positive sending reputation with Mailbox Providers. Sending activity from a new IP address can seem suspicious. Depending on the size of your sending list, warming can take an average of four to eight weeks. Warming could also take longer if providers do not perceive your mail is “wanted” by recipients. Some providers limit senders to specific thresholds until a stable reputation is established. 

Inbox Rev recommends starting off with your best-performing campaigns. You should focus on warming your most engaged subscribers while adding older segments as you progress. Older components should be added in bundles of 15% of your existing volume. The goal is to send to subscribers who are least likely to complain or bounce. This will include those who opted-in most recently and are consistently opening your mail and clicking. During your warmup phase, the more consistent you are with volume, frequency, complaints, and bounce levels, the faster you will establish a positive sending reputation.

An example of an IP warming outline would look something like this: During the first two weeks, send campaigns to your MOST ACTIVE subscribers – those who have opened/clicked in the past thirty days. During the next two weeks, extend to the subscribers who opened/clicked in the past sixty days. Follow this pattern until you have incorporated your entire sending list. During the first six weeks, DO NOT send to subscribers who have not opened or clicked in the last ninety days. 

Furthermore, once you begin warming your IP, you can expect some bulking and blocking to occur. Bulking at Yahoo!, AOL, and Gmail typically clear up after a few campaigns are sent with positive metrics. Delays at AOL, Comcast, and Microsoft (“421” Bounces) will typically retry for seventy-two hours. These delays are normal and will diminish as your reputation develops. However, if they are timing out in large quantities, you should back down your volumes to that provider by tightening up your engagement metrics. 

Possible blocking can also occur if your list isn’t engaged enough. Segment carefully and tighten up engagement. It is important to monitor your metrics and adjust the plan accordingly. Remember that engagement and consistency are key to a successful IP warm-up. If you are still unsure of the next steps or would like expert guidance during this process, contact Inbox Rev for assistance.

5 Tactics to Overcome Deliverability Challenges

Kristen Wyatt on June 21, 2023

All marketers would love for their campaigns to be delivered to the inbox and opened by all of their recipients. In reality, this is not the case. There are multiple challenges that email marketers must overcome. This blog post will focus on the 5 tactics that marketers can use to overcome email deliverability challenges.

Check your HTML and Plain Text versions

Filters like to see a plain text alternative. HTML version-only emails are a red flag for spam filters. Ensure that your Plain Text version matches the HTML version. Many platforms don’t always copy the text over on new email templates. Plain and simple, some people prefer text emails.  Since a variety of email clients give their users the option to only receive the plain text version of an email, it’s important to send campaigns in a multi-part MIME format.  If your subscribers have enabled this setting and you only send an HTML version, they may not receive your mail.

Review daily campaign and deliverability reports

It is critical that all email marketers review their campaign reports inside their ESP (Email Service Provider) on a daily basis. Look for and review specific metrics that could signal an immediate deliverability issue.  That would include:

  • Hard bounces – This bounce rejection reason from the recipient mail server indicates a permanent delivery failure.  Retried delivery attempts will not be successful.  An example of a hard bounce would be a bad mailbox.
  • Soft bounces – This bounce rejection reason from the recipient mail server indicates a transient delivery failure.  Retried delivery attempts may be successful.  An example of a soft bounce would be a mailbox full.
  • Unsubscribes – The number of email recipients that have clicked the unsubscribe link at the bottom of the email.
  • Complaints – Those email recipients that have clicked the Spam button inside of their email client.

Test and review all email signup forms

Email signup forms are another critical component to email deliverability that many email marketers don’t think about. Are you making sure that these email forms work? Do they collect the appropriate data? Do these email forms comply with all of the domestic and international email compliance laws?

Test the unsubscribe link

Do you use a one-click opt-out option or a preference center? Do you even know how your unsubscribe process works? Continuous testing of the unsubscribe link is crucial for Deliverability. If the unsubscribe link is not working, many email recipients could be clicking the spam button to get off of your list. It is also a best practice to include other ways for subscribers to follow you, including social media. Some subscribers would prefer using social media to get updates from you, instead of email.

Sign up for Google Postmaster Tools

Gmail has stated that less than 0.1% of email in the average Gmail inbox is spam.  Historically, Gmail has not offered any insight into email metrics for senders.  The Gmail feedback tool was launched a few years ago, but the tool is offered in the form of aggregated spam statistics, which cannot be traced back to the email address of the recipient who marked the mail as spam.  Google states that these Postmaster Tools are for qualified high-volume senders, like email service providers, to monitor senders closely.  By visiting https://www.gmail.com/postmaster/, high-volume senders can get email specifics including data on delivery errors, spam reports, and reputation.

To get started, there is a 3-step process to get the dashboard set up.  You will need to prove that you own the domain by entering the DNS TXT Record or the DNS CNAME Record.  The TXT record should not be removed after Google verifies it.  According to Google, it will be tested periodically to make sure the domain still belongs to you.  Once it’s verified and emails are flowing, you will get access to the data that Gmail is sharing about your deliverability.