How do email soft bounce retry policies affect domain reputation and deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 12 Jul 2025
Updated 19 Aug 2025
7 min read
Email soft bounces are a common occurrence for any sender. Unlike hard bounces, which indicate a permanent delivery failure (e.g., an invalid email address), soft bounces are temporary issues. These can stem from a full mailbox, a recipient server being temporarily down, or even content filters flagging your message.
When an email soft bounces, your email service provider (ESP) or mail transfer agent (MTA) typically implements a retry policy. This means they'll attempt to resend the email multiple times over a defined period, hoping the temporary issue resolves. While this sounds like a sensible approach to ensure delivery, the specifics of these retry policies can have a nuanced impact on your domain's reputation and overall deliverability.
Understanding how these retry attempts are handled, and how mailbox providers interpret them, is crucial for maintaining a healthy sending infrastructure. An overly aggressive or poorly managed retry policy can inadvertently signal to ISPs that you're not adhering to best practices, potentially leading to deliverability issues.
Understanding soft bounces and retry mechanics
Soft bounces occur for various reasons, often indicated by a 4xx SMTP error code. Common scenarios include the recipient's mailbox being full, their server being temporarily unavailable, or the message exceeding size limits. Sometimes, a soft bounce can also be due to greylisting, where the receiving server temporarily rejects an email from an unknown sender and asks the sending server to retry later to verify its legitimacy.
ESPs (Email Service Providers) are designed to manage these temporary failures automatically. They implement retry schedules, which dictate how many times and over what period an email will be re-attempted. For instance, some providers might retry every 15 minutes for up to 72 hours, as documented by platforms like Salesforce. This automated process is meant to maximize delivery for legitimate emails that encounter transient issues.
It's important to distinguish between retry attempts for a single email send and soft bounce tolerance across multiple campaigns. The former is defined by the SMTP protocol (as per RFC 5321), where the sending server retries a single message. The latter, however, is an ESP-specific mechanism where a subscriber is marked as undeliverable after a certain number of soft bounces over consecutive campaigns. For example, Salesforce defaults to at least three bounces over 15 days before setting an address to held status.
Impact on domain reputation and deliverability
While individual soft bounces (or transient failures) typically have a minimal immediate impact on your sender reputation, a high volume of them, or persistently retrying emails to addresses that consistently soft bounce, can eventually degrade your standing with mailbox providers. ISPs, like Gmail or Yahoo, monitor your sending patterns closely. If they observe an excessive number of retries or a high soft bounce rate over time, it can be interpreted as a sign of poor list quality or aggressive sending practices.
A key concern is when soft bounces start to trigger throttling or rate limiting by ISPs. This means the recipient server is deliberately slowing down or temporarily refusing your emails, often as a signal that your sending behavior is suspect. Persistent throttling indicates an underlying reputation issue that could impact your overall domain reputation, not just for the soft bouncing addresses but for your entire sending stream.
Risks of aggressive retries
Lower inbox placement: Mailbox providers may start routing your emails to the spam folder or blocking them outright, even for valid recipients.
Blocklist (blacklist) inclusion: If retries are seen as excessive or abusive, your IP or domain could end up on an email blacklist (or blocklist), severely impacting your ability to deliver emails.
Wasted resources: Continually attempting to deliver to non-responsive addresses consumes valuable sending capacity and can skew your deliverability metrics.
Furthermore, if you're promoting time-sensitive content, emails that are continually deferred by long retry policies may arrive too late to be relevant. This leads to a poor recipient experience and diminished campaign effectiveness, regardless of whether the email eventually lands in the inbox. It is essential to ensure that your bounce management is robust.
Optimizing soft bounce retry policies
While it's generally advisable to rely on your ESP's default retry policies, especially for large, reputable providers, it's beneficial to understand their logic. Many ESPs have optimized these settings based on extensive data and experience with various ISPs, ensuring a balance between persistence and good sending etiquette.
However, if you're observing persistent soft bounces or suspect your retry policy is contributing to deliverability issues, consider discussing this with your ESP. You might be able to adjust the soft bounce tolerance, which determines how many times an address can soft bounce across different sends before it's suppressed from your list. A higher tolerance might be appropriate if you send infrequently, to avoid prematurely removing valid subscribers. Conversely, if you send frequently, a lower tolerance might be better to maintain a clean list.
Recommended practices
Monitor bounce logs: Regularly review your bounce logs to understand the reasons for soft bounces and identify any recurring patterns.
Adjust suppression logic: Implement (or adjust with your ESP) a robust soft bounce suppression logic that moves consistently soft bouncing addresses to a suppressed state after a reasonable number of attempts or a certain period. This prevents continued, fruitless sending.
Segment based on engagement: Instead of relying solely on bounces, segment your list by engagement. Regularly re-engage or remove inactive subscribers to reduce the likelihood of soft bounces caused by abandoned or inactive mailboxes.
Long-term strategies for healthy deliverability
Managing soft bounce retry policies is just one piece of the puzzle for maintaining excellent email deliverability. The overarching goal is to send only to engaged, valid recipients, ensuring that your sending reputation remains pristine. This proactive approach minimizes the chances of encountering soft bounces in the first place, reducing the need for extensive retry policies.
Continuously monitoring your email program's health is paramount. Utilize tools that provide insights into your bounce rates, sender reputation, and inbox placement. Google Postmaster Tools, for example, offers valuable data on your domain's reputation and deliverability performance, allowing you to identify trends and address potential issues before they escalate. Consistent monitoring helps you understand how your emails are being received by ISPs and implement adjustments as needed.
Ultimately, a well-managed email program, characterized by strong sender authentication (SPF, DKIM, DMARC), high list quality, and relevant content, will naturally minimize soft bounces and optimize deliverability. Retry policies are a necessary component of email delivery, but they work best when complemented by robust sending practices that foster a positive sender reputation from the outset.
Views from the trenches
Best practices
Actively manage your subscriber list by regularly removing unengaged or invalid addresses to reduce future soft bounces.
Understand your ESP’s default retry and suppression policies and align them with your sending frequency.
Segment your audience and tailor content to improve engagement, naturally reducing bounce rates.
Regularly monitor deliverability metrics including bounce rates, spam complaints, and inbox placement.
Implement email authentication protocols like SPF, DKIM, and DMARC to build sender trust.
Common pitfalls
Ignoring persistent soft bounces, which can accumulate and negatively impact your sender reputation.
Overly aggressive retry policies that can lead to being perceived as a spammer by mailbox providers.
Not distinguishing between a single email retry and soft bounce tolerance across multiple campaigns.
Failing to suppress addresses that consistently soft bounce over several sending cycles.
Prioritizing sending volume over email list hygiene and audience engagement.
Expert tips
Your ESP's default retry policy is usually well-calibrated based on extensive industry data, so generally trust it.
Focus more on your overall soft bounce tolerance across campaigns rather than individual retry intervals.
Consider a higher soft bounce tolerance if you send emails infrequently (e.g., monthly) to avoid excessive list churn.
A lower soft bounce tolerance is better for frequent senders to maintain list hygiene.
Be cautious of emails perpetually deferring; this could indicate a deeper reputation issue.
Marketer view
Marketer from Email Geeks says that while ESPs often retry soft bounces many times, this typically does not impact reputation, comparing it to an MTA checking if a recipient is home before delivering a package.
2019-06-27 - Email Geeks
Marketer view
Marketer from Email Geeks says that the retry policies implemented by major ESPs, such as Salesforce Marketing Cloud, are generally standard and well-optimized by their deliverability teams.
2019-06-27 - Email Geeks
Maintaining a healthy sending reputation
Soft bounce retry policies are an essential part of email delivery, designed to recover messages that encounter temporary issues. While individual retries generally don't harm your reputation, an accumulation of soft bounces or overly aggressive retry patterns can indeed negatively impact your domain's standing with mailbox providers. They can lead to throttling, reduced inbox placement, and even blocklisting (or blacklisting).
The key is to understand both the technical aspects of retries and your ESP's soft bounce tolerance across multiple campaigns. By maintaining a clean, engaged email list, continuously monitoring your deliverability metrics, and allowing your ESP to manage the intricate retry logic, you can ensure that soft bounces don't become a detriment to your sending reputation and overall email program success.
Gmail or 
Yahoo, monitor your sending patterns closely. If they observe an excessive number of retries or a high soft bounce rate over time, it can be interpreted as a sign of poor list quality or aggressive sending practices.
