Why some customers get your newsletter twice

Getting the same email twice is a small thing for a customer, and it repeats with every campaign you send. It makes your list look bigger than it is, and on some plans it adds to your bill. You can fix it without changing anyone’s consent.

Why it happens

The usual cause is one person with two subscribed addresses. That often traces back to two Shopify customer profiles: one from a guest checkout with a work email, another from an account with a home email. A customer who moved to a new address and subscribed again does the same.

Typos rarely cause double sends, since a mistyped address usually never receives anything. They cause the opposite problem: a customer who asks why they never get your emails.

In MergeGuard’s demo store: 1,012 subscribed contacts → 926 people; 86 would get the newsletter twice Demo store (Northsail Supply).

What it costs

• Every send goes out twice to those people, for as long as both addresses stay on the list.
• Your numbers drift. Opens and clicks are spread across two addresses for one reader.
• Your bill may grow. On a plan priced by contacts or sends, duplicates count. See how email platforms bill for contacts.

The same thing happens off-screen. One merchant found they had been sending duplicate print magazines to the same person (merchant report).

What it can do to complaints and deliverability

No study we found ties duplicate profiles to complaint rates, so this section is reasoning, not a finding. Google’s sender guidelines say to keep your Postmaster Tools spam rate “below 0.10%” and to avoid ever reaching 0.30% or higher, and Yahoo’s bulk-sender rules say to keep it below 0.3% (Google, Yahoo). Each extra copy of a campaign is one more chance for the same person to mark it as spam, and a person who receives every campaign twice has more reasons to.

Leave the extra address out of your sends

Unsubscribing a contact changes their consent record. Leaving an address out of your sends doesn’t. When a person is subscribed twice, they agreed to hear from you, so the tidy fix is to send to one address and quietly skip the other. The steps above work that way.

If you merge the Shopify profiles

Merging puts the person’s orders and details on one customer, which stops the split at its source. Two rules from Shopify’s Help Center matter here:

• “After the profiles are merged, you can’t reverse the process.”
• “If the customer is subscribed to email and SMS text marketing in one profile, but not in the other, then the merged profile is subscribed.”

The second rule cuts both ways. If someone unsubscribed on one address and is still subscribed on the other, the merged customer ends up subscribed. Check which choice is more recent before you merge, and keep a note of it. Klaviyo’s own profile merge is permanent too, and its Help Center says consent and suppression information is merged along with the profiles (Klaviyo). A wrong merge of two different people could subscribe someone who never agreed, so leave close calls separate.

For more on keeping a list clean, see list hygiene.