A soft bounce is an email that reaches the recipient’s mail server but is temporarily undeliverable. This means the email address is valid, and the server is functioning, but some temporary issue prevents delivery. Unlike hard bounces, which indicate permanent delivery failures, soft bounces suggest that the email might be deliverable at a later time. Email Service Providers (ESPs) typically retry sending soft-bounced emails for a certain period, usually up to 72 hours.
Common Causes of Soft Bounces:
- Full Mailbox: The recipient’s mailbox has reached its storage capacity and cannot accept new messages. This is a common reason for soft bounces, especially for personal email accounts with limited storage.
- Server Issues: The recipient’s mail server might be temporarily unavailable due to maintenance, overload, or technical difficulties. This is usually a short-term issue that resolves itself quickly.
- Message Too Large: The email message exceeds the size limit set by the recipient’s mail server. This can happen if the email contains large attachments or embedded images.
- Temporary Server Outage: The receiving server might be experiencing a temporary outage or downtime.
- Spam Filtering (Temporary): Some aggressive spam filters might temporarily reject an email if it triggers certain spam indicators, even if it’s not spam. This is less common but can occur.
Why Soft Bounces Matter:
- Impact on Deliverability (Less Severe than Hard Bounces): While soft bounces don’t damage your sender reputation as severely as hard bounces, a high soft bounce rate can still negatively affect your overall deliverability.
- Missed Opportunities: If your emails are consistently soft-bouncing, you’re missing out on opportunities to connect with your subscribers and drive conversions.
- Indication of Potential Problems: A high soft bounce rate can be an indicator of underlying issues with your email list, such as outdated or inactive email addresses.
Distinguishing Soft Bounces from Hard Bounces:
The key difference lies in the permanence of the delivery failure:
- Soft Bounce: Temporary delivery issue. The email might be delivered later.
- Hard Bounce: Permanent delivery failure. The email will never be delivered.
Handling Soft Bounces:
- ESPs and Retries: Most ESPs automatically handle soft bounces by retrying delivery for a set period (usually 72 hours).
- Monitoring Soft Bounce Rates: Monitor your soft bounce rate to identify any trends or potential problems. A sudden spike in soft bounces could indicate a server issue or a problem with your email content.
- List Hygiene (If Persistent): If you consistently see high soft bounce rates for certain email addresses, it might be a sign that those addresses are becoming inactive or outdated. Consider removing them from your list to maintain good list hygiene.
Example Scenarios:
- A subscriber is on vacation and their mailbox is full. An email sent to them will soft bounce until they clear their mailbox.
- A recipient’s mail server is undergoing maintenance. Emails sent during this time will soft bounce until the server is back online.
- An email containing a large video file exceeds the recipient’s server’s size limit, resulting in a soft bounce.
Example of ESP Handling:
An email marketing platform sends an email campaign. Some emails soft bounce due to full mailboxes. The platform automatically retries sending these emails over the next 72 hours. If the mailboxes are cleared within this time, the emails will be delivered. If not, they might be categorized as bounced after the retry period.
Soft bounces are a normal part of email sending, but it’s important to monitor them and take action if you see consistently high rates. By understanding the causes of soft bounces and practicing good list hygiene, you can minimize their impact on your email deliverability and marketing performance.