We talk too much about send times, not enough about promises.

50 newsletters analyzed: when the title is a headache, it doesn't matter what day it is. Sunday evening, Monday morning, Thursday 2 PM. People click.

When the title is lukewarm, the perfect slot saves nothing. It's dead on arrival.

Tuesday 8 AM is comfortable because it's measurable. The promise, however, requires thinking about what your reader truly wants. Less fun to track.