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What’s the difference between a hard and soft bounce?

Dealing with spam filters can be tricky. Using spam filter testing tools is a great start to understanding your delivery and deliverability performance, but it’s important to see what happens after the send, too.

Enter: the bounce.

An email bounce is the technological equivalent to getting a letter marked “return to sender.” It means that your email wasn’t able to be delivered.

The terms “hard bounce” and “soft bounce” are commonly used as broad descriptions for whether or not the email address should be mailed to again at a later date. And while there can be lots of grey area around them from a technical standpoint, here’s what you need to know when it comes to adjusting your email marketing efforts:

What Is a Hard Bounce?

When we talk about hard bounces, what we’re talking about is a permanent bounce. This means that for whatever reason, an email will not be received by that email address.

A permanent bounce may be the result of an unknown user error, which is caused when an email address:

  • Is invalid because it doesn’t exist
  • Has been deactivated, such as when someone leaves a company or abandons a free email account
  • Contains a typo that made it invalid (i.e., typing instead of

When in the process of updating your email list, actively managing hard bounces is a critical step. While most ESPs can take care of this for you, it’s worth taking a look into your specific ESP’s practices, and ensuring that this process is in place.

If you’re handling bounces manually, you could delete the email addresses, but we recommend deactivating them or adding them to a suppression list as part of your list hygiene practices. Doing this removes the possibility that you will accidentally send to email addresses that you know will hard bounce.

What Is a Soft Bounce?

When we’re talking about soft bounces, what we’re talking about is a temporary bounce. A bounce that can be classified as temporary indicates that while the delivery of this current message was unsuccessful, you may be able to deliver another email to that address at a later date.

It could be bouncing because:

  • You have been blocked by the recipient’s inbox provider because too many users have marked your emails as spam.
  • You have been blocked for being on a blocklist
  • The recipient’s mailbox is full
  • The email account has been temporarily suspended
  • Of an unforeseen error or outage at the receiving mail server

Temporary bounces may not need immediate attention because they usually resolve on their own, but they should be closely monitored. Matt McFee, CEO of Briteverify, recommends treating soft bounces like hard bounces, and that after three bounces, it’s time to remove the email from your list. It’s also important to understand the interval in which those bounces happened: Was it over the course of a day or a week?

Where Do I Find This Information in My Reports?

While it varies by ESP, you can generally find bounce rate metrics in each individual mailing’s report, along with the rest of your delivery data. As an example, this is what ours looks like:

hard and soft bounces

From there, you can dig into either your hard or your soft bounces to see a full list of each recipient and their bounce code—which is the data you’ll need to start managing your list.

Time to Actively Manage Your Email Lists

When either a hard or a soft bounce occurs, it means it’s time to roll up your sleeves and dig into your lists. Repeatedly sending email to addresses that hard bounce can indicate to ISPs that you have bad list hygiene practices. We recommend reviewing your bounce stats at regular intervals on a weekly basis. Depending on the size and scope of your email marketing program, you may want to check more often, or more often during peak seasons.

Data quality is an important metric for ISPs when they’re deciding whether your emails are spam or not, and can contribute to your sender reputation.

Actively managing your list isn’t just good for deliverability, it’s good for engagement, too. (Which is, in turn, good for deliverability.) When you send to a cleaner list, you’re more likely to be sending to people who want to receive your email, and therefore are more likely to engage with it. That’s a win-win.

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