Wednesday, June 17, 2009

How To Analyze Bounces

Bounce rates are, in relation to emails, the number of email that do not get delivered and returns to the sender. There are many different reasons why an email fails deliverability. They can be divided into four different categories, which are:

1. Hard Bounce – Emails that are permanently undeliverable. Example; bad email addresses.

2. Soft Bounce – May not have a permanent reason for why the email is not going through. Example; full inbox, server is down or message is too large. Tip to keep in mind is to remove users after the 3rd soft bounce to avoid bad ISP reputation.

3. Blocks – Internet service providers reject emails due to spam filters. This can be due to black listed domains or when users manually mark domains as spam.

4. Other – Non-verified/Inactive accounts.

Usually when inquiring a bounce message you will receive some information to help the sender understand why your email was not delivered. Message may include:

  • Date and time of bounce

  • Identity of the mail server that bounced your email (

  • A reason/ error message (mailbox full or unknown user)

  • Header of the bounce message and some of the email content

If you are experiencing high bounce rate, a good step to keep in mind is to first clean your email list. Having a rate of 20% bounced emails is considered high. It is important to cleanse your mailing list and remove all email addresses that are misspelled, have bad domains and that are inactive. The more bad emails you have the higher the chances of having spam filters red flag you as using stolen or bought list leading to a higher spam score causing more bounces.

Having a low bounce rate is good only when you are satisfied with the size of your email list and when you know your message is actually delivered. There can also be the issue of having email testing as a false-positive (when your email is not rejected, but is directly filtered to Trash). Analyze your low bounce rate by checking in your major ISPs for open and click-through rates. This will help you uncover any underlying problem in misreading the reports of your low bounce rate.

Author: Adeline Zeledon
Editor: Yasifur Rahman

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