Most email deliverability failures aren't random. They're predictable — and preventable. Before your next campaign goes out, run through this checklist. Each item takes minutes. The alternative is watching a campaign land in spam with no idea why.
Before You Send: Authentication
1. Confirm your sending domain is authenticated
Your sending domain needs to pass authentication checks before any major inbox provider will trust it. If you're using Taildove, this is handled automatically when you connect your domain. If you're using another provider, check that your DNS records include SPF, DKIM, and DMARC entries — and that they're valid.
2. Verify your DMARC policy is in enforcement mode
A DMARC record set to p=none monitors but doesn't protect. Once you're confident in your authentication setup, move to p=quarantine or p=reject. This signals to inbox providers that you take your domain seriously.
3. Check your dedicated sending IP (if applicable)
Shared IP pools fluctuate in reputation based on other senders. If you're on a dedicated IP, check your IP reputation using tools like Sender Score or MXToolbox. If you've had recent deliverability issues, investigate before sending to your full list.
Before You Send: Your List
4. Remove hard bounces immediately
A hard bounce means the address doesn't exist. Sending to it again wastes resources and signals poor list hygiene to inbox providers. Any competent platform should suppress hard bounces automatically. Verify yours does.
5. Check your bounce rate from the last campaign
If your last campaign bounced more than 2%, investigate before sending again. High bounce rates are the fastest route to deliverability problems. Identify the source of bad addresses (a particular import, a specific signup form) and fix it.
6. Segment out long-inactive contacts
Contacts who haven't opened an email in 90+ days hurt your engagement metrics, which inbox providers use as a signal. Either run a targeted re-engagement campaign before your main send, or suppress them entirely.
7. Remove obvious spam traps
Spam traps look like real email addresses but are owned by blacklist operators. They're commonly found in old lists, scraped data, or purchased lists. If you're importing a list you didn't build organically, scrub it through an email validation service first.
Before You Send: Your Content
8. Test your subject line
Subject lines that look like spam get filtered like spam. Avoid all-caps, excessive punctuation, and phrases like "Act now" or "Guaranteed." Run an A/B test on subject lines if you have the list size for it.
9. Check your text-to-HTML ratio
Emails that are mostly images with minimal text are flagged by spam filters. Aim for at least 60% readable text. Every image should have a descriptive alt attribute.
10. Include an unsubscribe link
This isn't optional — it's required by CAN-SPAM, GDPR, and CASL. More practically, easy unsubscribes reduce spam complaints. Spam complaints hurt your reputation far more than an unsubscribe does.
11. Test across inbox providers
What renders beautifully in Gmail may break in Outlook. Send test emails to Gmail, Outlook, and Apple Mail before sending to your list. Most email platforms include an inbox preview feature.
Before You Send: Your Setup
12. Check your sending volume relative to your history
Sending to 10x your usual volume on a single day is a spam signal. If you're running a larger campaign than usual, consider segmenting it and sending over two or three days. Inbox providers reward consistency.
The Fast Version
If you're short on time, focus on the four that matter most:
- Authentication is configured and passing
- Hard bounces are suppressed
- Your list doesn't include inactive contacts from the last 90 days
- Your unsubscribe link works
Get these right and you'll be ahead of most senders.
Taildove runs several of these checks automatically — authentication, bounce suppression, and list hygiene at import. The rest is up to you. A few minutes before each campaign is worth it.