In Excel, add an Email column with the email addresses of the contacts to be opted out from receiving emails. Save the file in a CSV format.
Import your opt-out list
In your HubSpot account, navigate to Contacts > Contacts.
In the upper right, click Import.
Click Start an import.
Select An opt-out list.
Click select a file. In the dialog box, select the import file from your device.
Click the Email field column header dropdown menu and select the column header of the column in your import file that has the Email field.
In the bottom right, click Next, confirm your choice.
In the text field, enter the number of contacts to confirm they will be opted out from receiving emails.
In the bottom right, click Begin import.
Will these contacts count to your billable contact total?
Contacts who are imported on an opt-out list will not be added to your billable contact total because it does not create contacts in your HubSpot database. Instead, it marks the email addresses on the list as ineligible to receive emails from your account. These email addresses will be included if you ever export a list of bounced and unsubscribed contacts.
However, if there are email addresses in your opt-out import that currently exist as HubSpot contacts, while they will be automatically unsubscribed, they still exist as contacts and will count towards your billable contact total. To prevent these contacts from being included in your billable total, you can delete them and then re-import as an opt-out list. They will not exist as contacts in your portal, and only their email addresses will be marked as ineligible.
If your opt-out list needs to be imported from an external system on an on-going basis you could use an integration like PieSync to sync these email addresses to your HubSpot account.