For each delivered feature, there could be an overview, e.g.
"Users can now print reports easier. On our user request tracking platform, this issue had 321 upvotes, and 5 Premium clients requested this as well. We placed the print button THERE because amongst the three designs, this performed 23% better according to METRIC. For more info on the experiments, see link or ask on #mobile-team. The feature was released for two weeks behind a feature flag, it performed great, and we made it available for all since last Monday. 5%, of users who visited the report page used this feature and we generated already 5000 PDF reports. Big client A already complimented the feature, and it unblocked the sales process with Client B."
At the end of each email, there could be an analytics overview of the product with overall useful metrics, significant changes etc.
This format also helps with people being on holidays, sick, etc.