Unusual bounce increase

Level 1

Unusual bounce increase

Hi team,

Over the last 3 days my company has come across an increase of undelivered emails in Marketo and the main reason was for being added to a Spamhaus blocklist. We've checked our DNS, sender reputation and everything else and we don't see anything different compared to last week or even last month to justify such increase.

Is anyone having similar issue in Marketo? We are based in New Zealand, and we came across a 15/20% bounce rate.

Thank you!

Level 10 - Community Moderator

Re: Unusual bounce increase

If you’re using a standard shared Marketo instance, the IP reputation is naturally shared with every other tenant. So it doesn’t necessarily point to anything you have done.


At the same time, whatever sender reputation service you’re using is clearly insufficient, as it should be proactively monitoring the IPs you send from.


How have you determined for sure that you didn’t accidentally expand your audience, for example with a purchased list or people who didn’t opt in?

Level 10 - Community Advisor + Adobe Champion

Re: Unusual bounce increase

There are a few reasons you might be seeing a sudden increase in bounces due to Spamhaus even though your email practices seem consistent:

  • While you may not have intentionally changed your email content, it's possible a recent campaign or email element (like a specific image or link) tripped a filter.
  • If you're on a shared IP with other senders, their poor email practices could be impacting your reputation too.
  • Occasionally, Spamhaus can have temporary glitches that cause misidentification.

Here's what you can do to investigate further:

Here are some additional resources that might be helpful:

By taking these steps to identify the cause and working with Spamhaus if needed, you should be able to get your bounce rate back down.