How does CSA define stable sending patterns?

If you've ever sent a big promotional blast and noticed your open rates tank the next week, unstable sending patterns might be part of the reason. The Certified Senders Alliance (CSA) has a clear position on this: stable sending patterns are one of the foundations of a healthy sender reputation.

So what does "stable" actually mean? CSA defines it as consistent, predictable sending volume that changes gradually rather than spiking without warning. Think of it as a rhythm that mailbox providers can learn and trust. When your volume stays within a recognizable range week over week, inbox providers can make accurate decisions about your mail. When it suddenly jumps 500% in a day, they don't know if you're running a legitimate promotion or if your account was taken over.

That said, stable doesn't mean identical. CSA recognizes that normal business variation is expected. A retailer sending 20% more email in the week before Black Friday isn't a red flag. A SaaS company sending a burst of onboarding emails after a product launch isn't either. What matters is whether the change is gradual and explainable, not whether every Tuesday looks exactly like the one before.

Here's what CSA flags as genuinely problematic patterns:

• Sudden volume spikes with no warmup. Doubling or tripling your daily send volume overnight without gradually building to that level signals trouble. CSA expects volume growth to follow a ramp, not a vertical jump.
• Erratic on-off sending. Going silent for weeks and then sending aggressively is a pattern associated with compromised accounts and purchased lists. Consistent gaps followed by bursts look suspicious even if the total monthly volume is the same.
• Unexplained changes in sending frequency. Moving from weekly sends to daily sends in one step, without any ramp, is a pattern that degrades trust with mailbox providers who've built a baseline around your previous behavior.

In practical terms, "normal variation" tends to sit in the range of plus or minus 20-30% week over week without raising flags. That's not an official CSA number written in stone, but it's roughly the threshold where gradual growth stops looking gradual. If you need to scale past that, a proper warmup plan is how you get there without losing reputation points.

It's also worth noting that CSA's certification program isn't just about volume. Stable patterns support the broader framework of acceptable send velocity, which covers how quickly you can scale your sending without triggering filters. The two concepts are closely connected.

If you're unsure whether your current sending schedule looks stable to inbox providers, the blocklist checker can sometimes surface early warning signs. Or if you're dealing with something more complex, our SOS hotline is free and we'll look at your specific situation with you.