Send time optimization. I tested every hour and day. Here is what won

timing_tester · 2026-04-08 · 2,670 views

I ran a send time optimization test across 120K cold emails over 6 months. Every hour of every weekday, tracking reply rates by prospect timezone. Here's the data.

Best days: Tuesday and Wednesday. Reply rates on Tuesday and Wednesday were consistently 15 to 25 percent higher than other weekdays. My hypothesis: Monday is overwhelmed inbox day when everyone triages the weekend backlog and deletes cold emails without reading. By Tuesday and Wednesday, prospects are caught up and have bandwidth for new conversations.

Best times: 8 to 10am and 2 to 4pm prospect local time. The 8 to 10am window catches prospects during morning inbox processing before meetings start. The 2 to 4pm window catches the post-lunch return when people check email again before afternoon focus work. Reply rates in these two windows were 30 percent higher than other times of day.

Worst times: Monday morning, Friday afternoon, weekends. Monday before 10am: prospects are drowning in weekend email. Friday after 2pm: mentally checked out for the weekend. Weekends: cold emails get buried under Monday morning triage when they go back to work. Avoid these windows entirely.

Why timezone matching matters more than exact time. This was the biggest finding. An email sent at 9am EST to a prospect in London arrives at 2pm their time, which is after-lunch slump. An email sent at 3am EST to that same prospect arrives at 8am London time, right in the prime window. If your sending platform doesn't support prospect timezone detection, you're leaving reply rate on the table. Instantly and Smartlead both handle this automatically. Set your campaigns to send in prospect local time rather than your time.

The timing gap between best and worst sending windows was about 40 percent in reply rate. That's a huge lever that most teams ignore. Get timezone right and send on Tuesday or Wednesday at 9am or 3pm prospect local time. That's the whole playbook.