A single opt-in means that contacts will not be asked to confirm their subscription to your list. Once they submit your form, subscribers are added as “Active” contacts to your list right away.
This option is configured on ActiveCampaign forms. By default the double opt-in is turned on, but it can be disabled at any time.
Enabling single opt-in
1. Click on "Forms" from the left navigation menu in your account.
2. Click "Edit" next to your form.
3. Click the "Options" tab on the right side of your form editor.
4. Click the gear icon next to your "Subscribes to list" action located in the "Form Action" box.
5. A pop up window will appear. Click the toggle to turn the "Opt-in Confirmation" off.
6. Click "Save."