Recent Testing

Direct Mail Testing Update 

Slit and nest reply devices are common in the direct mail fundraising industry and have been a long-standing standard for MSB direct mail. For the majority of the past decade, MSB has incorporated slit/nest reply devices into all direct mail packages — meaning the reply device is cut off from the rest of the letter and nested inside the envelope along with the letter and courtesy reply envelope (CRE). The idea behind this approach is that making the reply device a separate element of the mail packet would make it more noticeable to the recipient. Perforated reply devices remain attached to the letter but can be easily removed along the perforated line and inserted into the CRE.  

MSB has begun working with a new print vendor, XBP, which has advanced quality control (QC) technology to ensure the various pieces of each mail packet are properly matched. This technology uses 2D barcodes to confirm that every letter, courtesy reply envelope (CRE), and outer envelope (OE) is correctly matched. If any element of a mail piece is detected as being incorrectly matched, the production line will stop until the issue is resolved. This additional QC step helps prevent mismatched inventory between MSB stations.   
 
To utilize this QC technology, XBP requires reply devices to remain attached to the main letter, separated by a perforation line rather than being slit and nested. We took this as an opportunity to test the long-held assumption that slit/nest reply devices provide a performance advantage.  

In the recent May 2026 End of Fiscal Year Add Gift campaign, we conducted an A/B test with the control group receiving the standard slit/nest reply device and the test group receiving the new perforated reply device. Our hypothesis was that the connection/inclusion format of the reply device would not materially impact response metrics at the scale of our campaigns, meaning that perforated reply devices would perform comparably to the standard slit/nest format.    

Results: The perforated test group showed higher average gift amounts and response rates than the slit/nest control group. The average gift was 8.97% higher among donors who received the perforated reply device, representing an average gift of $7.42 more than among donors who received the slit/nest reply device. Additionally, the perforated group had a 0.25 percentage-point higher response rate than the slit/nest group. While the difference was directionally positive for the perforated group, performance is not different enough from the slit/nest group to be considered statistically significant. 

Statistically, this test supports our continued use of perforated reply devices in place of slit/nest reply devices, The perforated group showed a higher response rate and average gift, and the response-rate difference was not statistically significant, providing no evidence of a statistically significant negative impact from the change.  

This is a significant operational win for MSB: We can continue using perforated reply devices and take full advantage of XBP's 2D barcode QC technology, strengthening the accuracy and quality control of our mail production without sacrificing campaign performance.   

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