7 Common Email Soft Bounce Reasons and How to Fix Them

Bounces are like the Grinch that steals your Christmas; they kill your email campaign’s performance and ruin your deliverability rates. To make matters worse, not all bounces are created equal. There are soft bounces and hard bounces. Hard bounces are emails that return after being sent to an address that doesn’t exist. It’s like sending a letter to a house torn down years ago. The address is gone, and so is your chance to connect with your audience. On the other hand, soft bounces are temporary issues. They return emails sent to valid addresses, but something is wrong on the recipient’s end. This could be anything from a full inbox delivery to a server down for maintenance. While the issues causing soft bounces aren’t immediate causes for alarm, they could affect your email campaign’s performance and overall deliverability if they persist. In this post, we’ll cover the top soft bounce reasons so you can get your emails back on track and improve your email campaign’s performance.

Inframail can help you on your journey to better email deliverability. Our email infrastructure solution gives you the tools to boost your email performance and get your messages to the right people.

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What is a Soft Bounce in Email Marketing?

When an email bounces, it can’t be delivered to an inbox. “Hard” and “soft” designate the two groupings of failures: more permanent and less permanent.

Understanding the Differences Between Hard and Soft Email Bounces

A hard bounce is an email that couldn’t be delivered for permanent reasons. Maybe the email’s a fake address, the email domain isn’t an actual domain, or the email recipient’s server won’t accept emails. There are lots of reasons that an email could be a hard bounce, but the core of it is that it’s a permanent failure.

A soft bounce is an email that couldn’t be delivered temporarily. An inbox may be complete, or the email file might be too large, among other reasons. If they get a soft bounce on an email sent, most email providers will continue to try to deliver the email over a few days. If the problems aren’t fixed, a soft bounce can become challenging.

7 Major Soft Bounce Reasons

1. DNS Errors: What Are They and Why Do They Happen?

DNS failure is a standard error caused by the receiving side. It indicates an issue with the Domain Name System; a message couldn’t be delivered then. The recipient’s email server was likely temporarily offline or misconfigured. If that is the case, delivery will likely be retried over the following days, and only if it fails multiple times will a hard bounce occur.

Common Email Transmission Errors: Identifying Non-Existent Domains and Handling Connection Timeouts Effectively

Sometimes, this error might also appear if the domain you send it to doesn’t exist. In such a case, there will be no future attempts, and you’ll need to look for other ways to contact a recipient.

Other errors can also occur during a transmission—for example, a connection may time out. In such a case, a server will likely retry several times later before giving up.

2. Your Email Is Too Large for the Recipient’s Mailbox

Just as mailboxes have capacity limits, individual messages are also often subject to limitations. And while your outgoing servers might allow some messages with large attachments, it might not necessarily be true for ISPs.

If a message cannot be delivered due to its size, many ESPs will retry sending it over a specific period—usually several days. It will be permanently rejected if it fails to deliver by that time.

3. The Recipient’s Mailbox Is Full

Most mail providers limit mailbox size to a certain point. Gmail, for example, gives its users 15GB of free storage, while Yahoo! Provides its users with 1TB of storage space. Once a user hits that limit, their mail provider won’t accept new messages, so messages will bounce.

For example, here’s the bounce message you’ll receive from Google if you’re sending mail to a recipient who’s reached their storage limit.

Managing Soft Bounces: When to Retry and When to Remove Inactive Emails from Your Mailing List

Because the recipient can free up storage at any time, your next email attempt might be successful—a classic soft bounce.

Still, if you continue to see the same error message over multiple sending attempts, there’s a chance you’re trying to reach an abandoned inbox, and you might want to remove the recipient from your mailing list.

4. Temporary Issues or Delays on the Receiver Side

Mailbox providers can experience temporary issues or a heavy load of traffic that can prevent your emails from getting delivered.

Let’s look at this bounce from Apple, for example:
smtp;451 4.7.1 Service unavailable - try again later

This bounce tells us that messages are not being accepted right now, but you might have success delivering the same message when you try again later. We occasionally see this for sends happening at the ‘top of the hour’ when many other senders worldwide are also aggressively sending to Apple, and Apple’s inboxes simply get overwhelmed with processing the incoming mail.

Suppose your email service provider is doing a good job handling bounces. In that case, they’ll spot a bounce like this one and automatically retry sending your email after a few minutes (so that you don’t have to do it manually).

5. Content-Related Soft Bounces

Mailbox providers might choose to bounce individual emails if your content looks suspicious.

Even though these are soft bounces (with bounce codes that start with a 4.X.X), you should take all notifications that hint at an issue with your content or your overall sender reputation seriously. If you don’t act, these bounces will likely be upgraded to a hard bounce—or even an entire ISP block. Don’t let that happen.

Troubleshooting Content-Related Soft Bounces: How to Avoid Spammy Triggers and Ensure Your Emails Get Delivered

Here’s what a content-related soft bounce might look like:
smtp;421 4.7.0 Our system has detected that this message is suspicious due to the nature of the content and/or the links within. To best protect our users from spam, the message has been blocked. Please visit https://support.google.com/mai... for more information. - gsmtp

With this bounce, Gmail makes it clear that it isn’t happy with the content of your email. So it’s time to investigate:

Are you using any language that might come across as spammy?
Where are your links going?
Are you linking to websites that aren’t secure or come across as phishy?
Are you using link shorteners like bit[.]ly?

6. Spam or Reputation-Related Soft Bounces

In addition to email content, mailbox providers use other insights to decide whether or not you’re a trustworthy sender. If they’re suspicious of your sending reputation, they might decide to bounce your emails:

smtp;421 4.7.0 [TSS04] Messages from 0.0.0.0 temporarily deferred due to user complaints - 4.16.55.1; see https://postmaster.yahooinc.com/error-codes

Yahoo told you they received many spam complaints from emails originating from your domain, which could now affect deliverability for all messages from this sending IP. You should immediately look at what might be causing them.

7. Autoresponder Has Been Triggered

Often, sending to a large group of recipients will result in a wave of autoresponders hitting your inbox. This is especially true during the holiday season. These messages often inform you that the recipient is currently out of the office and will get to your message a bit later.

In such cases, the message has arrived in their inbox anyway, so there’s nothing you have to do. It won’t hurt to follow up a few days after they’re back if you don’t hear from them until then.

Leveraging Autoresponders for Contact List Maintenance: How to Keep Your Email Outreach Up-to-Date

It’s worth reading such autoresponders, as sometimes they may inform you that someone you’re writing to has moved on to a different company and no longer reads these messages.

Companies tend to keep such mailboxes alive and leave instructions on who to contact instead. If that’s the case, update the contacts on your mailing list.

How Can I Troubleshoot My Soft Bounces?

If you’ve been sending emails to a list with too many invalid addresses (which results in hard bounces), you’ll need to stop and take a breather before you send any more emails. That’s because hard bounces can affect your deliverability rates and cause emails to go to the wrong places.

If you have a high bounce rate, you’ll send a red flag to ISPs that you’re sending to a poor mailing list and might be spammy. Prune that mailing list to deliver relevant content to subscribers who want my messages to avoid this. You’ll also want to protect your sign-up forms to prevent some of these non-existent email addresses from making it into your email list in the first place.

Spam Complaints Can Cause Soft Bounces, Too

Not all subscribers want your messages. They may mark your message as spam if they don’t remember signing up for your list or can’t find an unsubscribe button. Spam complaints send a red flag to service providers. Some ISPs, like Yahoo, state in their bounce message that your email is temporarily deferred due to user complaints.

Reduce spam complaints and avoid the spam filter by using a double opt-in subscription option. This ensures your subscribers know they’re signing up for my mailing list. In addition, I offer a straightforward way to unsubscribe by providing all my emails, including an easy-to-find unsubscribe link. This way, your email recipients won’t mark my messages as “spam.”

Your Server Might Be Blocklisted

Your IP and domain reputations are important factors determining your email’s deliverability. ISPs may blocklist your IP or domain based on your sender’s reputation. This means they won’t deliver messages from your IP address or domain. After identifying and addressing the root issues for the blocklisting, you can either request a delisting or wait for automatic removal.

Low User Engagement Can Lead To Soft Bounces

Some ISPs interpret low user engagement to mean that your emails don’t contain high-quality content, which can result in a soft bounce. Employ strategic engagement by targeting specific audiences and using list segmentation to be more relevant to your subscribers. And, as always, it’s good practice to prune my mailing lists to remove disengaged users occasionally.

Your Recipient’s Inbox Might Be Full

One of the most common soft bounce reasons is that your recipient’s inbox is full. This usually means your recipient provided an email address they frequently use for unwanted marketing promotions. You can fix this issue by cleaning up my mailing list, employing segmentation, and ensuring my users double-opt into my emails. I’ll also want to ensure my emails provide value to the reader—this way, they won’t want to miss my messages in their inbox.

Too Many Emails Can Cause Soft Bounces

We know sending too many emails to senders who have previously opted in is not spamming, but… let’s be honest, sometimes it feels like that. Maintain a consistent volume for your messages, and don’t send emails too often. Some ISPs, like AOL, block or delay non-whitelisted IP addresses when they detect spikes in email sending volumes.

Start Buying Domains Now and Setup Your Email Infrastructure Today

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Agencies
Recruiters
SDRs

Main benefits of using our service:

Automated SPF, DKIM, and DMARC setup
Dedicated email servers for each user
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Unlike traditional providers that charge per inbox and leave you wrestling with technical configurations, Inframail streamlines the entire process. We handle the complex infrastructure setup while you focus on reaching more prospects. InfraMail provides a robust email infrastructure without the usual technical headaches and per-inbox costs, whether you're:

An agency looking to scale outreach
A recruiter connecting with candidates
An SDR driving sales

Start buying domains now and set up your email infrastructure today with our email infrastructure tool.

Bounces are like the Grinch that steals your Christmas; they kill your email campaign’s performance and ruin your deliverability rates. To make matters worse, not all bounces are created equal. There are soft bounces and hard bounces. Hard bounces are emails that return after being sent to an address that doesn’t exist. It’s like sending a letter to a house torn down years ago. The address is gone, and so is your chance to connect with your audience. On the other hand, soft bounces are temporary issues. They return emails sent to valid addresses, but something is wrong on the recipient’s end. This could be anything from a full inbox delivery to a server down for maintenance. While the issues causing soft bounces aren’t immediate causes for alarm, they could affect your email campaign’s performance and overall deliverability if they persist. In this post, we’ll cover the top soft bounce reasons so you can get your emails back on track and improve your email campaign’s performance.