Most deliverability damage is preventable. It happens because senders skip the basic checks before pressing send on a major campaign. The checks themselves take fifteen minutes. The damage from skipping them can take three months to recover from.

This piece is a practical pre-send deliverability checklist. Not the long, technical version that gets written for IT teams. The short, operational version that a marketing manager can run through before a campaign goes out the door.

Run it on every campaign that goes to more than 10,000 subscribers. Or on any campaign where the cost of landing in the spam folder is meaningful (a product launch, a major announcement, a time-sensitive promotion).

The segment check

Is the segment you are sending to actually engaged?

Before sending, pull the segment's engagement profile. What proportion has opened anything in the last 30 days? 90 days? 12 months? If a meaningful portion has not engaged in the past year, that segment is going to carry negative signals into the send.

The fix is straightforward: split the campaign. Send the main version to subscribers who have engaged in the last 90 days. Send a separate re-engagement-style version, or simply suppress, the segment that has not.

Is this segment size consistent with your usual sends?

Sudden volume changes look suspicious to inbox providers. If you usually send to 30,000 subscribers and this campaign is going to 80,000, that scale-up is itself a deliverability risk. The usual cause is a list import or a merge that has not been validated.

If volume is genuinely increasing, ramp it up across multiple sends rather than in one jump. A 30 percent volume increase per send is roughly the upper limit of what most providers will tolerate without flagging.

Are there any subscribers in the segment who should not be there?

Check for two specific categories before sending: hard-bounced addresses still in the active list (sometimes they get re-added inadvertently), and subscribers who recently complained or unsubscribed but were not fully removed (some platforms keep them in segments unless explicitly excluded).

Both categories cause disproportionate damage relative to their size. A handful of complaint-prone subscribers can tip the complaint rate above the threshold that triggers reputation impact.

The authentication check

Are SPF, DKIM, and DMARC all aligned?

Run a quick test send to a personal address on Gmail, Outlook, and Apple Mail. Inspect the headers. All three authentication results should show pass. If any show neutral, none, or fail, the deliverability of the main send is going to be affected.

This check should be standing infrastructure, not a per-campaign task. But the check is worth running before a major send because authentication can break for non-obvious reasons (an IT change, a domain renewal, a new tool added to the stack).

Is the from address consistent with previous sends?

Changing the from address on a major campaign is one of the most reliable ways to land in spam. Inbox providers track sender reputation against specific from addresses. A change resets the reputation. If a change is needed (rebrand, team change, address rationalisation), warm the new address with smaller, highly engaged sends first.

Is the sending domain warmed for the volume you are about to send?

A domain that usually sends 10,000 emails a day cannot suddenly send 200,000 without consequences. If volume is going to spike on a particular campaign, split the send across hours or days. Most providers handle higher volumes gracefully if the ramp is gradual.

The content check

Have you sent this exact email to yourself and clicked every link?

The number of campaigns that ship with one broken link is higher than anyone wants to admit. Broken links are not just a user-experience problem. They generate clicks that go nowhere, which can be interpreted as suspicious by some filtering systems, and they irritate subscribers, who are more likely to mark the next email as spam.

Send the email to a personal address before the campaign goes out. Click every link. Check the unsubscribe link works. Check the images render. Check the email displays correctly on at least one mobile device.

Are there any spam-trigger patterns?

Modern spam filters are less keyword-driven than they used to be, but certain patterns still cause problems: excessive use of capital letters in the subject line or first line, multiple exclamation marks, large blocks of red text, all-image emails with no text, very short emails with a single image and a link.

A quick scan for any of these patterns before sending takes thirty seconds and prevents a meaningful proportion of avoidable spam placements.

Is the unsubscribe link easy to find?

Hidden unsubscribe links are a deliverability problem masquerading as a retention tactic. Subscribers who cannot easily unsubscribe will mark the email as spam instead, which damages deliverability for everyone on the list. A clearly visible unsubscribe link in the footer protects the rest of the programme.

The warning signs check

Are there any warning signs from recent sends?

Before pressing send on a high-stakes campaign, look at the trends from the last three to five sends:

• Has the open rate been declining steadily? (Even slightly.)
• Has the bounce rate been creeping up?
• Have unsubscribes been increasing?
• Have any campaigns triggered higher-than-usual spam complaints?

Any of these signals suggests that sending more volume to the same list will compound the problem. Better to investigate the warning signs first, then send the campaign.

Has anything changed in the sending stack?

New tool added? New IP? Domain configuration change? Any of these can affect deliverability in ways that are not immediately visible. The pre-send check is the moment to think through what has changed and whether it has been tested at scale.

Where Mail Blaze fits

Mail Blaze surfaces several of these checks automatically. The List Health Check flags subscribers likely to bounce or complain before the send. The send preview lets you test how the email renders across major clients. Authentication status is visible from the campaign dashboard rather than buried in settings.

The point of the checklist is not to make the platform do the work. It is to make the marketer's last pass before sending a deliberate one. The platform handles the diagnostic; the marketer makes the call.