Klaviyo Email Deliverability: The 6-Point Checklist That Keeps You Out of Spam

Why Klaviyo Email Deliverability Tanks in Q4

Mailbox providers treat Q4 like a fire drill. Volume spikes, new senders, holiday promos, the whole internet is sending at once.

Gmail, Outlook, and Apple Mail all tighten their filters in October. Stores that were landing in the inbox in September suddenly watch their open rates drop 30% overnight.

We have seen this across 2,000+ Shopify stores. The stores that fix their Klaviyo email deliverability before October 15 own BFCM. The ones that wait pay the price.

This is the exact 6-point checklist we run for every client. Every check takes under 5 minutes.

The Klaviyo Email Deliverability Checklist That Protects Q4

Six points. Each one is non-negotiable. Skip one and your campaigns land in Promotions.

1. Branded Sending Domain With SPF and DKIM

Without a branded sending domain, Klaviyo sends from their shared infrastructure. You inherit the reputation of every other Klaviyo sender. That is fine until one of them goes on a spam run.

Set up a branded sending domain in Klaviyo:

1. Go to Account, then Settings, then Domains and Hosting
2. Click Add a Branded Sending Domain
3. Enter your domain (for example send.yourstore.com)
4. Add the SPF and DKIM TXT records Klaviyo gives you to your DNS
5. Wait 24 hours, click Verify

Once verified, switch every flow and campaign to send from the branded domain. Do this before your next big send.

2. Klaviyo Smart Sending Activated

Smart sending prevents Klaviyo from hitting the same profile more than once every 16 hours. Without it, a profile triggering two flows on the same day gets 4 emails in 6 hours. That is a fast track to spam complaints.

Enable smart sending by default on every flow email that is not transactional. Turn it off only for order confirmations and shipping updates (those always need to send immediately).

3. Consistent Sender Name and Domain

Mailbox providers track sender reputation per From identity. Change your sender name in the middle of Q4 and you reset your reputation to zero.

Pick one sender identity for the entire quarter. Example: Jip from Ecomflows from hey@send.ecomflows.io. Every campaign, every flow, same identity.

4. Kill the Spammy Subject Lines

Spam filters are trained on decades of data. They know what spam looks like.

Avoid all of these:

• ALL CAPS subject lines
• Multiple exclamation marks
• Words like FREE, DISCOUNT, WINNER, SALE written in caps
• Emojis stacked in the subject line (one is fine, five is spam)
• Subject lines with mismatched preview text

Write subject lines like you are texting a friend. Quick question about your cart outperforms 50% OFF TODAY in 9 out of 10 tests.

5. Exclude Bounced and Unengaged Profiles From Every Send

Hard bounces are permanent deliverability damage. Every send to a bounced profile is another vote against your domain reputation.

Build a universal exclusion list and apply it to every single campaign template:

• Hard bounced in last 90 days
• Soft bounced 3+ times
• Unengaged segment (received 5+, opened 0)

Klaviyo lets you save this as a default exclusion at the account level. Do it once, it applies everywhere.

6. Keep Your Open Rate Above 20%

20% is the line. Above it, you are safe. Below it, filters start pushing you to Promotions.

The 20% rule is not a Klaviyo rule, it is a mailbox provider rule. Gmail and Outlook both use engagement rate as a primary spam signal. Your Klaviyo dashboard is the reflection, not the cause.

If your open rate is below 20%, work backward through this checklist. Points 1 through 5 will get you to 20% within 2 to 3 sends.

What to Do If Klaviyo Email Deliverability Is Already Broken

If you are sending below 15% open rate, pause all campaigns for 7 days. Seriously.

Sending more to a broken reputation only deepens the hole. Use the pause to:

1. Suppress unengaged profiles
2. Verify your branded sending domain
3. Clean your flow exclusions
4. Rewrite your next 5 subject lines to look like personal emails
5. Come back with a small send (under 10% of list) to engaged openers only

After 7 days, your reputation starts to recover. Build volume back up gradually, starting with your most engaged 20%.

The One-Page Summary

SPF and DKIM configured. Smart sending on. Consistent sender identity. Clean subject lines. Bounced and unengaged excluded. Open rate above 20%.

Six checks. 30 minutes of work. Protects your Q4 revenue.