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Time to read: 4 minutes
We’re taking it back to the basics to define a term that is super important to email deliverability but still seems to cause some mailers a bit of confusion: email bounces. What’s the difference between a hard bounce vs. soft bounce?
At SendGrid, we probably position soft bounces a little differently. We look at soft bounces more as blocks—or short-term issues. These blocks shouldn’t be added to a suppression list. But, hard bounces (invalid email addresses and non deliverables) should be. Read on to learn about:
An email bounce signifies the non-delivery of your email message. When this happens, the mailer will receive an automatic notification of the delivery failure. This failure originates from the recipient’s mail server for a number of reasons (explained below).
Usually, the bounce message will give you important information to help you identify the reason for the email delivery failure. This includes the following:
At SendGrid, there are two types of bounces that you can receive—a soft bounce/block or a hard bounce. Think of soft bounces as blocks that are a short-term issue—you don’t need to permanently take these addresses off of your list. However, hard bounces are either invalid or non-existent addresses that should be removed immediately.
A soft bounce means that the email address was valid and the email message reached the recipient’s mail server. However, common reasons it bounced back include:
At SendGrid, we continue to attempt to send these messages for up to 72 hours until the message is delivered. If a message is continuously deferred for 72 hours, we convert these addresses to a block/deferral list. (A deferral list is not a suppression list.)
A hard bounce occurs when the message has been permanently rejected either because:
At SendGrid, we add these hard bounced addresses to a suppression list. What this means is that even if you send a message through us for that user, we will not even try to deliver to that address, because we know it’s no longer good. Continuing to try to send to a known bad address will harm your reputation with the receiver, so we prevent that.
The best way to reduce the number of bounces is by following some key email deliverability best practices. This includes the following:
Achieving high email delivery rates can be a challenge, but not if you know the ropes. For more tips, download our best practices guide: Tips and Tricks to Stay Out of the Spam Folder.
A hard bounce indicates that an email has been permanently rejected either because the recipient's email address is invalid or does not exist. On the other hand, a soft bounce signifies a temporary delivery issue, such as a full inbox or a server temporarily unavailable. Hard bounces should be removed from your mailing list immediately to maintain a healthy sender reputation, whereas soft bounces can generally be retried within a short period.
A soft bounce is typically indicated by a 4XX SMTP error code in your email bounce reports. Common reasons for a soft bounce include a full mailbox, large message size, or the recipient's server being temporarily down. The bounce message will often provide the specific reason and the error code.
A soft bounce in your email campaign might temporarily impact your deliverability. It suggests a short-term issue with the recipient’s email server or mailbox. Monitoring the frequency and reasons for soft bounces can help you take proactive measures, such as resizing emails or rescheduling sends, to improve deliverability and guarantee your communications reach the recipient (eventually).
To reduce soft bounces, keep your email sizes within acceptable limits and clean up your maling lists—you want to avoid sending to full inboxes or temporarily unavailable servers. Regularly clean your email lists and segment them based on engagement.
Want to lower your email bounces and bump up your deliverability rates? Sign up for a free Twilio SendGrid account and let us help you make it happen. We can empower your email program with email list hygiene tools, double opt-in features, delivery analytics, and more.
Partner with the email service trusted by developers and marketers for time-savings, scalability, and delivery expertise.