Understanding Soft Bounces in Email Marketing: Causes and Solutions

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Email marketing is a powerful tool for engaging with customers, but it’s not without its challenges. One common issue marketers face is email bounces, particularly soft bounces. Unlike hard bounces (which indicate permanent delivery failures), soft bounces are temporary delivery issues that can often be resolved.

What Is a Soft Bounce?

A soft bounce occurs when an email is temporarily rejected by the recipient’s mail server. Unlike a hard bounce (which means the email will never be delivered), a soft bounce suggests that the issue may be resolved, and future delivery attempts could succeed.

Key Differences Between Soft and Hard Bounces

Soft Bounce	Hard Bounce
Temporary issue	Permanent failure
May resolve on retry	Will not resolve
Common causes: full inbox, server issues	Common causes: invalid email, blocked domain

Common Causes of Soft Bounces

Understanding why soft bounces occur helps in preventing them. Here are the most frequent reasons:

1. Recipient’s Mailbox Is Full

Many email providers (e.g., Gmail, Outlook) impose storage limits. If a user’s mailbox is full, incoming emails may bounce temporarily.

2. Server Issues or Downtime

If the recipient’s email server is down or overloaded, emails may not be delivered immediately, resulting in a soft bounce.

3. Large Email Size

Emails with heavy attachments or high-resolution images may exceed size limits set by the recipient’s server, causing a temporary rejection.

4. Content Filtering Issues

Aggressive spam filters may temporarily block an email if it contains certain keywords or formatting that trigger suspicion.

5. Temporary Authentication Problems

If your domain’s SPF, DKIM, or DMARC records are misconfigured, some servers may temporarily reject your emails.

How to Reduce Soft Bounces in Email Campaigns

While some soft bounces are unavoidable, you can minimise them with these best practices:

✅ Maintain a Clean Email List

• Remove consistently bouncing emails after multiple attempts.
• Use double opt-in to ensure valid addresses.

✅ Optimize Email Size

• Keep attachments under 10MB (or smaller, depending on ESP limits).
• Compress images and avoid excessive HTML.

✅ Monitor Sender Reputation

• Avoid spammy content and high complaint rates.
• Warm up new IPs gradually if switching email providers.

✅ Improve Email Authentication

• Set up SPF, DKIM, and DMARC to improve deliverability.
• Use a consistent “From” address to build trust.

✅ Retry Strategically

Most Email Service Providers (ESPs) automatically retry soft bounces for a set period (e.g., 24-72 hours). If the issue persists, treat the email as a hard bounce.

When to Remove Soft Bounce Emails from Your List?

While soft bounces are temporary, repeated failures indicate a deeper issue. Consider removing an email address if:

• It soft bounces 3+ times in a row.
• The same address repeatedly bounces across campaigns.

Keeping too many soft-bouncing addresses can hurt your sender reputation and deliverability.

Soft bounces are a normal part of email marketing, but managing them effectively ensures better deliverability and engagement. By maintaining a clean list, optimizing email content, and following authentication best practices, you can reduce soft bounces and improve campaign performance.

Pro Tip: Regularly audit your email list and monitor bounce reports to stay ahead of deliverability issues.