When you create multiple lists to segment your contacts, a single contact can be added to as many lists as you want. If you send an email to several lists and a contact appears on more than one of them, we automatically prevent them from receiving duplicate copies of your email. We also have safeguards in place to prevent you from adding duplicate email addresses to your account when you add or import contacts.
Even with processes in place, a contact could still receive multiple copies of an email. Here are a few possible causes, along with how you can fix them:
We define a contact by their email address, not their name. If the same person has signed up for your list multiple times with different email addresses (leigh.grammer@gmail.com, lgrammer@outlook.com, etc.), they are treated as separate contacts. If you send an email to a list or multiple lists that include these different email address variations, a copy of your email is received at each address.
To prevent the email from being received multiple times, remove duplicate contacts from your list. You can delete the extra contact or merge the information together.
After you send an email, you can always copy it to resend it. If you send the copy to a new list and a contact is on both the original and the new list, they will receive two copies of the emails.
To prevent this, use the Resend feature to send your email to the new list. If a contact received the first email and is also on your new list, they won't receive it again.
You can create your own A/B test to see how just about anything in your email performs with your audience and use the results to increase your open rate. If you send an email to your "A" list, copy it, and then send it to your "B" list, duplicate emails will be sent to a contact who is on both lists.
To prevent duplicate emails from being received, compare both contact lists and remove the duplicate contacts from one of the lists before performing your A/B test.
 | Did you know? When you use our Subject Line A/B Test feature, your A list and B list never receive the same email, and a contact never appears on both lists. |
If your contact has multiple email addresses and sets up automatic forwarding from one address to another, they'll see the email in both accounts if you send to the address with forwarding enabled. If your contact isn't sure whether they have forwarding enabled, have them check their email client settings and disable it if it is.
More often than not, the contact's server or firewall is the reason they're receiving duplicate emails. Unfortunately, there is nothing you, as the sender, can do in this case, but we can further investigate for you.
 | Important: Before contacting Support, you'll need to obtain the message headers for each of the problematic emails. Message headers let us see any patterns or error messages that may shed some light on the root cause of the problem. |
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