Every email marketer has sent the wrong thing to the whole list. The five minutes before you press send are the cheapest quality control available, and almost nobody uses them systematically.
This is the checklist in the order that catches the most problems soonest.
Content
- Click every link. Every one, including the logo and the footer. A broken link in the main call to action is the most expensive mistake on this list and the easiest to prevent.
- Check the links go where the copy says. A link labelled as one thing pointing at another is a phishing pattern and a scored negative signal, as well as a broken promise.
- Read the subject line and preview text together, as they appear in an inbox. Many clients show both, so a preview repeating the subject wastes the most valuable line you get. See email preview text.
- Check merge tags with an empty record. Preview as a subscriber with no first name. "Hi ," reaching 4,000 people is a merge tag failure, and previews with populated test data never reveal it.
- Check every dynamic branch, including the default. See dynamic content.
- Verify prices, dates, deadlines and discount codes. Actually try the code.
- Read it aloud once. It catches things reading silently does not.
Rendering
- Outlook on Windows. The one that will break. Word's rendering engine ignores margins and background images — why your email looks broken in Outlook.
- Gmail web and Gmail mobile.
- Apple Mail on iPhone.
- Dark mode, in at least Apple Mail and Outlook.com, because they invert differently.
- Images off. Does the email still say what it is and what to do? Is the alt text real copy?
- At 200% zoom or with large system text, which a meaningful share of readers use.
Send a real test to real addresses rather than relying on the platform preview. Previews render in a browser and skip the client transformations that cause most of these problems.
Deliverability
- Authentication passes. Send to a Gmail address, open "Show original", confirm SPF, DKIM and DMARC all read PASS. If SPF passes and DMARC fails, that is an alignment problem — see SPF, DKIM and DMARC explained.
- Run a spam check. Not because a score predicts the inbox, but because it flags obvious problems: bad ratios, blacklisted link domains, missing text part.
- Check the text-to-image ratio. An email that is one large image with a line of alt text is the classic spam pattern.
- Read the plain text part. Auto-generated text versions from image-heavy HTML are often nearly empty, which is a small negative signal and a real problem for screen readers. See plain text vs HTML email.
- Unsubscribe link present and working. Click it from a test address and confirm the suppression landed.
The send settings people forget
This is where the genuinely embarrassing mistakes live, because they are outside the email itself and nobody looks at them twice.
- The right segment. Read the segment name, then read the recipient count. A count ten times larger than expected means the segment is wrong.
- Exclusions applied. Recent purchasers excluded from the acquisition offer, current customers excluded from the trial pitch.
- Suppression list active.
- From name and reply-to. Does a reply go somewhere a person reads? A no-reply address on a campaign inviting replies is a recurring own goal.
- Schedule. Right date, right time zone. Time zone errors are the single most common scheduling mistake.
- Tracking and UTM parameters present, so the campaign is attributable — otherwise you will not be able to calculate its conversion rate afterwards.
The one-minute version
If you only have sixty seconds: click the main call to action, check the recipient count and segment name, preview with an empty first name, and confirm the subject line is the one you meant. Those four catch most of what actually goes wrong.
Frequently asked questions
What should I check before sending an email campaign?
Links, merge tag fallbacks, rendering in Outlook and on mobile, dark mode, images off, authentication, and — most importantly — the recipient count and segment. The send settings cause more damaging mistakes than the email content does.
Why does my email look fine in preview but broken when sent?
Platform previews render in a browser and skip client-specific transformations: Outlook's Word engine, dark mode inversion, image blocking and Gmail's CSS handling. Always send a real test to real accounts.
Do spam checker scores predict inbox placement?
No. They flag content-level problems like poor text-to-image ratios and blacklisted link domains. Actual placement is decided mostly by sender reputation, authentication and recipient engagement, which no content scanner can see.
How many test sends should I do?
One properly checked test to a set of real addresses covering Outlook, Gmail and Apple Mail beats five casual ones to a single account. What matters is the coverage of rendering engines, not the number of sends.
