Spam Complaints Tell a Story

Chris Kolbenschlag, Director of Deliverability

Many times marketers send an email campaign and quickly move on to the next campaign only looking back to see what the open, clicks and conversion rates were. These metrics are key to reviewing the success of the campaign which is important, but it’s critical to also look at any negative repercussions of that campaign and learn from it.

Spam complaints are when a user (at Hotmail, Comcast or certain other ISPs) receives an email that is unwanted and clicks on the ‘this is spam’ button’ within the UI. This in turn notifies the ISP that this email is unwanted and that ISP will send that email back to the sender. In general, marketers want to reduce spam complaints, so be sure to read this post on ways to reduce complaints.

When this communication system was created between senders and ISPs, it wasn’t initially intended for the sender to just remove these people complaining and remove the squeaky wheel. It was created so that the sender can monitor feedback from the subscribers to see how that specific campaign did in comparison to previous campaigns. For example, if a sender sends out daily to their entire list and that send generates 100 complaints each day then all of a sudden the same daily send to the same group generates 300 complaints, this spike is an indication there is a problem with that send. This is the exact data that marketers often miss and this data is telling an important story that we should listen to.  If you see such a spike, here are some questions and ideas on why it happened and what to look at.

New Additions

Did you add any new group of email addresses lately? Yes? Where did they come from? Was it a co-reg with unclear expectation of who would be sending to them. Did you run a contest and add those addresses into your list? Was it an old list of people you haven’t emailed for a while or maybe a list of people who signed up many months ago and never mailed to them.

Collection Methods

Did you make any changes to your email address collection methods? Is the sign-up process clear, with listed expectations (daily, weekly, coupons, tips etc). Are you auto opting in people after they make a purchase without notifying them of the sign up? Are you pre-checking an opt-in box on behalf of the client? While growing your list is important, be careful if it’s bringing in complaints.

From Address

Did you change your ‘friendly from’ or ‘from’ address? Subscribers become accustomed to a brand name and/or from address and changing this can create some mistrust in who the email is from.


Did you increase frequency? If you increased your weekly frequency to a daily send while this could increase ROI, in the end you can lose subscribers due to the increase of emails to their inbox. Also offer a preference center and allow subscribers to select their own cadence.


Did you change your message? I signed up for a cycling newsletter that had important information on cycling in regards to nutrition, techniques and a few ads on new bikes. Over time, the newsletter became mostly ads and offers for bike trips to Europe and hardly anything I initially signed up for and they lost me as a subscriber. Keep your word and offer what people signed up for.


Are you using segmentation? For example, are you sending aftershave offers to your entire audience including females? Make each email relevant and important to the individual subscriber and not just a blanket message.

Issues with Certain Campaigns

Which campaigns are causing these complaints? Welcome emails? Could be a sign-up problem with unclear consent or expectations. Transactional? Transactional messages should have a primary purpose of a notification of a transaction such as a purchase but can take on a marketing feel of trying to up-sell heavily and loses its message. Also, the number of messages sent for just one transaction can overwhelm a buyer. Newsletters? Could be the newsletters are becoming stale or irrelevant.

Who’s Complaining?

  • Are the people complaining new subscribers? Points to email address collection (co-reg, auto opt-in, pre-check boxes) or unclear expectations.
  • Are the people who complain contacts who have been around a while? Your relationship may have run its course. Maybe it’s time to break up with these subscribers?
  • Are they non-engaged email addresses? Points to irrelevant, stale content/offers. Send them an opt-in request to stay and remove non-responders.
  • Are they subscribers you haven’t mailed to in a long time because your site wasn’t ready or you just forgot about them? Re-introduce yourself.
  • Are the complaints coming from a list you collected via a contest or sweepstakes? Make it an opt-in versus opt-out when they enter their address.
  • Did this group sign up in the store for a quick 10% at the register? Offer an incentive to stay on with you and not just a one time offer.

This may all look and sound overwhelming but it is such an important piece to look at when reviewing each of your email campaigns. Spam complaints are the #1 killer of a sender’s reputation and it is vital to minimize these complaints as much as possible in order to get your emails into the inbox of those who do want to hear from you.

Chris Kolbenschlag
Director of Deliverability at Bronto

  • Greg Kraios

    As always, great information here Chris!

    I would also add that it’s important to identify where subscribers originate from (website, in-store, customer service calls, trade shows, etc.) so mailers can track which collection methods are the most successful, cause the most issues, etc.

    These things often get ignored which makes tracking down and correcting the issue more difficult.

  • Chris Kolbenschlag

    Hey Greg!
    Thanks for the reply.

    Excellent addition to tracking down the source of these complainers. This can be a big eye opener to pinpoint where the trouble originated from and/or continues to come from.
    It all starts with permission and knowing exactly where the each subscribe came from it vital.
    Thanks again Greg!

  • I got an email from you today. I checked…I don’t have any other emails from in my inbox and it goes back (not counting archives) to September 2010.

    Yet you emailed me. Best Practices? Really? And instead of a single click opt out you send me to a Managed Preference Center?

    You guys fail miserably IN YOUR OWN INDUSTRY!!!

    • Michael Ballard

      Today we sent a message in error due to a segmentation mistake. It’s our fault and we’re really sorry that recipients received a message that they didn’t sign up for. This is not a normal occurrence, rather an anomaly in our sending process. The email you received was meant for subscribers who have opted in.

      Again, we are very sorry that you received an unwanted email and hope that you can understand the reason.