What are best practices for continuous monitoring?
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How often should you actually be checking your deliverability? That depends almost entirely on how often you send, and how much volume you're pushing.
If you're sending daily or near-daily, a daily check of your core metrics is worth it. Spam rate spikes, open rate drops by provider, and bounce increases can compound fast at high volume. Catching something on Tuesday instead of Friday is the difference between a minor fix and a serious reputation problem.
If you're a weekly sender, a weekly review after each send is the right rhythm. Check Gmail Postmaster Tools (spam rate and domain reputation) and Microsoft 365's SNDS (Smart Network Data Services) at a minimum. These two cover the majority of your subscribers' inboxes. If anything looks off, dig in before your next send, not after.
Campaign-based senders (newsletters, event emails, one-off sends) should review within 24 to 48 hours of each send. That window captures the freshest engagement signal. Run a seed list test before major sends, not just after problems appear.
What you're actually watching for:
- Spam rate trending above 0.1% in Gmail Postmaster (the threshold that starts hurting you)
- Open or click rates dropping suddenly for a specific mailbox provider (Gmail fine, but Yahoo dropping could mean a placement issue)
- Bounce rate climbing (especially hard bounces, which signal list quality problems)
- Domain or IP reputation moving from "High" to "Medium" in Gmail Postmaster
So the difference between a metric that matters and normal variance is trend vs. snapshot. A single low open rate on one campaign isn't a fire alarm. A three-week slide in open rates is. Track these numbers over time, not just as one-off readings. Most ESPs let you export this data or build dashboards around it.
Set up automated alerts where you can. Spam rate alerts inside your ESP, reputation drop notifications via Postmaster, and blocklist checks are all worth configuring so you're not relying on manual memory to catch problems. You can run a quick blocklist check on your domain any time you suspect something's off.
The goal isn't to be glued to dashboards every hour. It's to have a rhythm that matches your send cadence, so nothing drifts without you noticing. Gradual declines are as dangerous as sudden drops. They're just quieter about it.
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