A/B Testing Email Send Times: Does It Actually Matter

What the Research Actually Says

Every year, email marketing platforms publish "best time to send" studies that claim to have found the optimal send window. The results are contradictory and unhelpful: one platform says Tuesday at 10 AM, another says Thursday at 2 PM, and a third says it does not matter at all. The reason for the conflicting data is that the "best" send time depends entirely on your specific audience, their habits, their time zones, and your relationship with them.

A B2B audience of office workers checks email during business hours, so a weekday morning send might outperform a weekend send. A B2C audience of parents might check personal email in the evening after their kids go to bed. A list of freelancers might check email at unpredictable times throughout the day. No universal "best time" exists because different audiences have different email habits.

This is exactly why you test. Instead of following generic advice, you send the same email to two random segments at different times and measure which segment has higher engagement. After running this test a few times, you will know when your specific list is most receptive, which is the only data that matters.

How to Set Up a Send Time Test

A proper send time test requires you to isolate the time variable from everything else. Send the exact same email, with the same subject line and content, to two randomly selected segments of your list. The only difference should be the time of delivery. If you change the subject line or content between the two sends, you have contaminated the test and cannot draw conclusions about timing.

Start by testing large time differences rather than small ones. Test a morning send (9 AM) against an afternoon send (3 PM) or a weekday send against a weekend send. Large time gaps are more likely to produce detectable differences. Testing 9 AM against 10 AM is unlikely to produce meaningful results because the behavioral difference between those two times is minimal for most audiences.

Once you find a general window that works (say, weekday mornings outperform weekday afternoons), you can run a follow-up test within that window to narrow it down further (Tuesday morning vs. Thursday morning, or 8 AM vs. 10 AM).

Time Zone Considerations

If your list spans multiple time zones, a single send time means different recipients receive your email at different local times. An email sent at 10 AM Eastern arrives at 7 AM Pacific, which might be too early for West Coast recipients. Most email platforms offer time zone-adjusted sending, where the email goes out at 10 AM in each recipient's local time zone.

If your platform supports time zone sending, test whether it improves performance. In some cases it does, particularly for B2B lists where business hours matter. In other cases the improvement is negligible because many people check email outside of business hours anyway. The only way to know for your audience is to test it.

When Send Time Testing Is Not Worth It

If your list is small, say under 2,000 contacts, send time tests are unlikely to produce statistically reliable results because the expected difference between times is smaller than the random variation in a small sample. Focus your limited testing capacity on subject lines and content format, which produce larger, more detectable differences.

If you send infrequently, say one campaign per month, spend your testing capacity on the content of that campaign rather than its timing. The content you send matters more than when you send it. A great email sent at a suboptimal time still outperforms a mediocre email sent at the "perfect" time.

The Real Priority Order

If you are choosing what to test first, here is the order that produces the most value for most teams:

1. Subject lines, because they determine whether anyone opens at all
2. Email content and format, because they determine whether anyone clicks
3. CTA text and placement, because they determine whether anyone takes action
4. Send time, because it provides a modest incremental improvement once the above are optimized

Send time is worth testing, but it belongs after the fundamentals. Get your subject lines, content, and calls to action right first. Then optimize timing to squeeze out the last few percentage points of performance.