The Monthly Check That Keeps a Sending Domain Healthy

SPF, DKIM, and DMARC records can drift out of alignment without anyone changing them on purpose: a new sending tool gets added without updating SPF, a DNS provider migration drops a record, or a DMARC policy someone tightened for a different reason starts quarantining legitimate cold sends. Check all three every month with a free authentication checker rather than assuming they're still configured the way they were when first set up.

A misaligned record doesn't always throw an obvious error; it can just quietly lower deliverability instead of blocking sends outright, which is exactly why nobody notices until the audit catches it.

Run the sending domain and its IP against the major public blocklists once a month, since a domain can land on one without a single bounce notice reaching you directly. Some blocklists are minor and low-impact; others are used by major mailbox providers and will quietly route your mail to spam the moment you're listed.

Finding out from a blocklist check is far better than finding out because a prospect mentions your email went to spam, which usually means the problem's been running for weeks by the time you hear about it.

Send a test email to a set of seed inboxes across the major providers, then check whether each one landed in the primary inbox, a secondary tab, or spam. This is the only check that tells you what a real recipient actually sees, since authentication and blocklist status can both look clean while inbox placement has still quietly degraded.

Run this test with the actual template and sending pattern you're using in live campaigns, not a stripped-down test message, since the real content and cadence are part of what's being evaluated.

Pull the last three months of bounce rate and spam-complaint rate side by side rather than looking only at the current month in isolation. A slow upward creep across three months is a real signal worth acting on even if any single month's number looks fine on its own; a one-month spike after a big send might just be an unusually large batch and not indicate a genuine health problem.

Set a simple internal threshold for each metric that triggers an immediate deeper look rather than waiting for next month's scheduled audit.

None of this works if it depends on someone remembering to run it. Put a recurring calendar reminder on the same day each month, assign it to one specific person, and keep the actual checklist in a shared doc so it survives a handoff if that person changes roles.

A five-item checklist that runs reliably every month catches almost every real deliverability problem before it costs meaningful pipeline. The same checklist run inconsistently, or not at all, is why domains end up in real trouble before anyone notices.

The monthly checklist, in the order to run it:

1. Re-verify SPF, DKIM and DMARC records with a free authentication checker instead of assuming they are still configured correctly.
2. Check the sending domain and its IP against the major public blocklists.
3. Send seed tests to inboxes across the major providers and note whether each landed in primary, a secondary tab or spam.
4. Review the last three months of bounce and spam-complaint rates side by side to catch a slow upward creep.
5. Pause sending from any affected domain the same day a failed check or blocklist hit turns up, and document what broke.

Finding an issue during the monthly check is the good outcome, not the bad one, since it means the problem gets fixed while it's still small. Pause active sending from an affected domain the same day a blocklist hit or a failed authentication check turns up, rather than letting new sends go out while the underlying cause is still being diagnosed.

Document what broke and why in the same shared doc that holds the checklist, so the next audit, and the next person running it, has a record of what's already gone wrong once and what fixed it.