Yes. Open the campaign and toggle A/B test on. Create two variants — typically two subject lines, or two different message bodies.
Senly sends variant A to 10% of your list and variant B to another 10%. After 4 hours, Senly checks which variant had the highest open or click rate and automatically sends that winning variant to the remaining 80%.
Works best from 200+ recipients — below that scale, statistical significance is too low.