If an e-mail address in your list ceases to be valid, you remove it from the list. Simple enough, right? There are more subtle aspects of bounce management that you might not be acutely aware of, however.

A bounce is a notification that your message, for whatever reason, didn’t make it to the recipient. Ideally, these bounces take the form of SMTP codes.

Using these codes, ISPs (Internet Service Providers) can communicate the reason for the bounce. Not everyone follows this standard however, and accurate bounce handling may involve some keyword review of the replies.

Regardless of the bounce message’s exact wording, there are two types of bounces: hard and soft. Depending on whom you talk to, they might have more technical definitions; but here is the gist of what they mean.

A hard bounce means; either the receiving server purposely rejected the message or the receiving server doesn’t exist. Examples of hard bounces are:

  • The user doesn’t exist at the domain.
  • The domain doesn’t exist.
  • The message was rejected.

A soft bounce typically denotes a temporary error with delivery and may be any response other than a hard bounce. Examples of soft bounces are:

  • The e-mail server isn’t responding
  • The user’s mailbox is full.

Why Process Bounces?

It’s important to properly process bounces for a couple reasons. You don’t want to pay for e-mail messages sent to non-functioning addresses. If you don’t process bounces correctly, a mailing list’s natural churn will result in large portion of dead addresses on the list.

Monitoring bounces can help show a potential delivery problem. Perhaps an e-mail domain that represents a significant portion of your list has stopped responding. Perhaps your messages are being rejected. By monitoring bounces after every campaign, you can quickly correct any irregularities.

Most important, ISPs look at bounce information when determining whether they’re being targeted by a spammer. Spammers’ e-mail lists are of very poor quality. If an ISP detects a large percentage of invalid e-mail coming from one IP, the mail stream may be identified as spam and blocked.

Minimise Bounces

Here are some tips to help effectively deal with or minimise email bounces:

  • ISP’s recommend retrying hard bounces no more than three times. In our experience, retrying a hard bounce only once after a period of two to four days is sufficient.
  • Remove hard-bounced addresses from the list either immediately or after the retry attempt fails. Remove soft-bounced addresses from the list if the address repeatedly generates bounces over a period of four to five e-mail campaigns.
  • Scan keywords when processing bounces to help deal with non-standard bounce messages.
  • Use a double or confirmed opt-in subscription process to minimize incorrect and false addresses from the start.
  • Use an e-mail change of address service to help combat e-mail address churn in your mailing list.
  • Add an e-mail address update link to your e-mail and a profile update form to your Web site, enabling subscribers to update their address and preferences.
  • Consider contacting bounced subscribers via postal mail or phone (if you have contact information and permission) to obtain their new e-mail addresses.
  • To ensure subscribers enter their e-mail addresses correctly, include a script that checks for syntax errors upon submission. Additionally, consider requiring subscribers re-enter their addresses in a second box.
  • Monitor bounce messages (particularly from key ISPs and domains) for signs of e-mail rejection. The message may have been rejected due to blocking or filtering and you may need to contact the administrator of the receiving system.
  • Monitor bounce rates continually, and establish a benchmark. Analyze the cause, and take appropriate action when a message lies outside of the norm. Though average bounce rates can vary dramatically, if your rate continually rises above 5 percent, you may have list input or hygiene issues.
  • Pre-test messages for potential spam-oriented content to help minimize rejections by ISP and corporate spam filters.

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