Sender Score: Keeping an Eye Out for Red Flags

Here at Return Path, we often refer to Sender Score as a credit score for your IP address—however this is not the only way to understand this critical component of sender reputation. Consider for example that hot, new restaurant that has opened in town, with reservations booked months in advance. What would happen if you just showed up on a Friday night with a group of 15 people? Let’s say you showed up wearing a muscle shirt and sneakers, when a jacket and tie are required for entry? Or perhaps the hostess remembers all too well “Polka-Dot Dorothy”, that mean nickname you called her in high school. By nature, all of these elements come together and ultimately contribute to whether or not you will be allowed to dine at the restaurant.

In this scenario – consider the restaurant is the mailbox provider, and Polka-Dot Dorothy is the gateway, the deciding factor on whether or not you will enter. Your inappropriate outfit, large party, and presence on a personal blacklist are all factors contributing to your poor reputation. Let’s take a step back though – what if you didn’t know that there was anything wrong with your behavior? Wouldn’t it be easier if there was a way to monitor your reputation, so you would have an idea if you would be allowed in the restaurant? Knowing in advance that your behavior was wrong would give you an opportunity to break out that old red-suede suit from the bottom of your closet, and ensure your entrance into the restaurant.

The value of Sender Score
Sender Score measures your IP address reputation on a scale of 1-100, and is representative of the overall health of your email program. This score is calculated using a proprietary algorithm, assessing metrics that are important to both mailbox providers and your subscribers. In addition to providing a numerical score, Sender Score also gives you a breakdown of key reputation metrics, and ultimately gives you an indication of whether your message will end up in the Inbox, Spam folder, or be blocked completely. Keep in mind that Sender Score can fluctuate frequently, and is calculated on a rolling 30-day average overall. Anyone can look up their Sender Score by IP address at
SenderScore.orgReturn Path customers can find additional information within the Reputation Monitor product inside the Email Optimization Tool Suite.

Sender Score: Diagnosing red flags
In order to effectively use Sender Score, it’s important to know which deliverability red flags to look out for, and how to use them to diagnose larger problems within any email program. To explore the potential of Sender Score, we’ll be walking through several examples of reputation red flags and what you can do to avoid them. The examples below are all real examples that were discovered by Return Path employees during routine account monitoring. Keep in mind that the below screenshots are pulled from Reputation Monitor and not – while displays general details of high-level metrics, Reputation Monitor will offer more robust data including numerical values, rates, trends, and thresholds.


1. Use reputation data to check for spikes in Unknown Users
In order to increase the chances of successful inbox placement, the amount of Unknown Users is just one of the deliverability metrics that should be kept consistently low. One of the easiest ways to monitor Unknown Users is to keep an eye out for any spikes by using Sender Score and Reputation Monitor. If you do see a spike in this metric, it’s a good indication that it’s time to clean out your email list and remove any subscribers that aren’t regularly engaging with your brand. Unknown User spikes are often accompanied by spikes in volume—these spikes generally mean that an older and larger list was added to your regular pool of subscribers. If including these older subscribers periodically is unavoidable, consider engaging in a list cleanse before hitting “send”. Cleaning your list takes the guess work out of which addresses are still active and which are not—and can help you avoid tanking your reputation by including these dead addresses on your send.

Unknown Users                                                                                                 




2. Keep an eye out for increasing Spam Traps
Spam Traps are another metric that should be kept at or as close to 0 as possible. Unknown User’s big bad older brother – Spam Traps are addresses used by mailbox providers to identify senders with poor list hygiene. Similar to a spike in Unknown Users, an increase in Spam Traps can mean that your inactive subscribers aren’t being suppressed at reasonable intervals. It can also mean that Unknown User bounces are not being automatically removed – something that countless Return Path clients have been able to uncover by tracking their Spam Trap data. Hard bounces should be removed immediately, and it’s always a good idea to double check that this process is being followed by your ESP. When monitoring Spam Traps, it’s important to note that there are a few key differences in data presentation depending on whether you are using or Reputation Monitor. Unlike, Reputation Monitor not only tells you the number of Spam Traps hit – it breaks this number down further into Pristine vs. Recycled Traps. Furthermore, Reputation Monitor showcases trap hits by date – making it much easier to investigate which segment of your list the trap might be hiding in.

Reputation Monitor                   











3. Be on the lookout for high complaints
Use and Reputation Monitor to track your subscribers’ complaint rate Complaints occur each time a subscriber marks or reports your mail as spam, and can have devastating impacts on deliverability if not addressed. Return Path and can help you keep complaint rates top of mind, and Reputation Monitor can help you identify patterns in complaint rates. The great thing about this tool is it will point senders towards messages sent during the same time period that the complaint was received, helping generate that additional ammunition needed to uncover the root cause of the complaint. Using complaint data from Return Path, one sender was able to identify that a particular message in their welcome series was garnering above average complaints, and was able to bypass users on this message to successfully reduce complaints. See below for an example of complaint rate trends within Reputation Monitor, and where to click to check out corresponding campaigns:


It’s important to remember that these red flags can only be discovered and fixed if you commit yourself to regularly monitoring your IP address reputation. There’s no magic button that can promise delivery to your subscriber’s Inbox 100 percent of the time, but keeping these reputation red flags top of mind can ensure you are prepared to fix any potential problems that may arise. After all, you don’t want to show up to dinner wearing those ugly sneakers again!

For additional information regarding Sender Score and reputation metrics, check out Return Path’s other blog posts, “Track and Monitor Your Reputation using Sender Score”, and “All About Your Sender Score”.

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