When an email message cannot be delivered to an email address, it's called a bounce. There are lots of different reasons why emails bounce so, when it happens, a "return to sender" message is sent from the recipient's mail server to explain why.
We process this information for you and put it together in the Bounce Summary section of your campaign report. On this page we'll explain what's in the report and how we handle bounced email addresses for you. We'll also look at the difference between soft and hard bounces.
Your campaign bounce rate
One of the most important metrics to monitor after you've sent a campaign is the "bounce rate," which is the number of bounced emails divided by the total number of recipients the campaign was sent to.
A bounce rate percentage is calculated for every campaign you send and displayed on the snapshot page of your campaign report, as shown here:
Note: It can take up to 12 hours for all bounced email addresses to appear in your report.
Bounce rates are directly related to the quality of your subscriber list. Low bounce rates are a sign of a healthy, permission-based list with active and engaged subscribers. High bounce rates indicate that there may be problems with the way your list was grown, or how it is being managed.
A healthy opt-in list should be seeing bounce rates of between 2-3%. If you are regularly generating higher bounce rates, it's important that you work out why and take action to reduce the number of bounces.
We can help you investigate the cause of high bounce rates and work out how to fix the problem, so please do contact us. If your bounce rates are regularly exceeding the industry standard of 2%, it may result in your account being suspended in which case we'll have to get in touch with you anyway.
What's in the Bounce Summary report
We use the bounce message returned from your recipient's mail server to classify each bounce as soft or hard, meaning a temporary or permanent delivery failure. The Bounce Summary shows you which email addresses bounced and why.
To find the bounce summary, click Bounced from the report snapshot (pictured above) or Bounce Summary in the right sidebar of your report. On the report page you can search bounces by recipient name or email address, as shown here:
Tip: Use the Export button, bottom-right, to download bounce data from each tab.
The Bounce domains tab (see above) shows you how many emails bounced for each domain you've sent to. This is useful for determining if you have delivery problems with any specific domains. If you notice a large number of bounces for one domain, it may indicate that your emails are being blocked by the ISPs receiving server.
ISPs and other mail systems check incoming mail from each source and can see if you're sending to a lot of addresses that are bouncing. If they detect that you are they'll start rejecting your campaigns on the assumption your list is made up of automatically generated or purchased emails. In other words, they may be blocking you on the assumption you're a spammer.
That said, if you find that almost all of your emails to a certain domain like @gmail.com or @aol.com are resulting in bounces, it may be because your content has been identified as spammy. In these cases, your best bet is to contact us so we can look at the kind of bounces you're receiving and investigate further.
Soft bounces versus hard bounces
When an email bounces it is classified as either a soft bounce or a hard bounce:
A soft bounce is a temporary delivery failure.
Your email campaign got as far as the receiving mail server, meaning the email address was recognized, but the message bounced back undelivered instead of reaching the recipient's inbox.
Soft bounces can occur when the recipient's mailbox is full; the receiving server is down or swamped with messages; the message size is too large; the recipient's settings do not allow for email from the sender; suspicious or spammy content has been detected, and many more reasons.
It does not necessarily mean the email address is invalid or no longer active, so while we have stopped trying to deliver your last campaign, we will try to send the next one to these addresses.
A hard bounce is a permanent delivery failure.
When you get a hard bounce it means the recipient's email address is invalid or no longer in use. Typically the domain name (the bit after the @) no longer exists or it no longer has registered mail servers. But it could also be invalid due to typos, for example gnail instead of gmail.
Email addresses that hard bounce are automatically removed from your subscriber list so you don't pay to send to them again. We also add them to your suppression list which prevents the addresses from being accidentally re-imported.
Note: Servers can sometimes interpret bounces differently, meaning a soft bounce on one server may be classified as a hard bounce on another.
When a soft bounce becomes a hard bounce
When an email address returns a soft bounce five times, with no opens or clicks recorded during that period, we automatically convert that address to a hard bounce.
When a subscriber interacts with an email, the number of soft bounces recorded for that address (if any) is reset to zero. Bounce handling is explained in more detail below.
How we handle bounces
We work hard to keep bounces as low as possible so we can deliver as many of your emails as possible. We constantly monitor the email acceptance rates of our outgoing IP addresses and use sophisticated algorithms to automatically adjust sending rates, as well as which sending IPs are used.
As mentioned earlier, when an email address appears in the Bounce Summary report it means we are no longer attempting to deliver your campaign to that address. However, unless it’s a hard bounce, we'll typically make 50 or more attempts to deliver your campaign.
When we determine that a recipient ISP appears to have temporary delivery issues we'll try resending after five minutes, and then (approximately) after every 15 minutes. We do not try for more than 12 hours to deliver a campaign because this ends up burying deliverability issues instead of alerting you to them.
When an email address has soft bounced for five campaigns in a row – and only when those five campaigns were sent over more than two days – we automatically convert the email address to a hard bounce and remove it from your list.
Important: Please be aware that moving hard bounced subscribers back to active status will negatively affect your deliverability. ISPs and spam filtering systems record instances of emails returned to senders and will judge all future emails from the sender much more harshly if the invalid address is emailed again.
I have an email address listed as a hard bounce, but I know it is valid. What happened?
It may be that the recipient's mail server sent us incorrect information about the status of their email address. Please contact us before trying to send another email to that address so we can investigate.
Does a bounce mean my email landed in their junk folder?
No. Bounced emails do not make it as far as the recipient's spam or junk folder. Emails that land in the junk folder do not appear in your Bounce Summary report, and we do not receive notifications when this happens.