What is 3-Wave Sending?
3-wave sending (also called phased sending or staged sending) is the practice of sending a single email campaign to three separate segments of your list in sequence, with monitoring between each wave. Instead of sending to all 100,000 subscribers at once, you send to 10%, wait and monitor, send to another 30%, monitor again, then send to the remaining 60%.
This approach lets you catch deliverability problems — high spam complaint rates, unexpected bounce spikes, or blacklisting — before they affect your entire list and sender reputation.
The Three Waves
Wave 1 — Probe
10% of your list — Most Engaged Subscribers
Send to your most engaged subscribers — those who opened or clicked in the last 30 days. This group is the least likely to complain and most likely to engage, giving you a clean early signal on deliverability. Wait 2–4 hours and check your metrics before proceeding.
Wave 2 — Validate
30% of your list — Active Subscribers
If Wave 1 metrics look healthy (open rate normal, bounces under 2%, spam complaints under 0.08%), proceed to Wave 2. Send to subscribers active in the last 90 days. Confirm deliverability holds at scale before the final push.
Wave 3 — Full Send
Remaining 60% — Full List
Send to your full remaining list — including less-active subscribers. By this point, you have validated that your campaign is clean, your authentication is working, and ISPs are routing your mail to the inbox. The full send is low-risk.
Stop Thresholds — When to Pause
If any of these thresholds are exceeded during Wave 1 or Wave 2, stop sending immediately and investigate before proceeding.
Bounce rate
>2%
Remove addresses and check import source for bad data
Spam complaint rate
>0.08%
Review subject line and list segment — something is mismatched
Open rate
>70% drop vs avg
ISPs may be filtering — check Postmaster Tools immediately
Blacklisting
Any new listing
Pause all sends, investigate source, request delisting
When to Use 3-Wave Sending
Use 3-wave sending for: campaigns to lists over 50,000 subscribers; first campaigns after a period of inactivity; campaigns with new or unusual content; sends after migrating to a new ESP; and any promotional campaign with high commercial intent (discounts, flash sales).
