When you use personalisation to display the value of a contact data field in a campaign, page, or form, a blank space is displayed if a contact doesn't have a value stored against it.
This is where a default value comes in handy. It's a value that gets displayed instead of a blank space. For example, if you personalise a campaign with Hi @FIRSTNAME@ but a contact doesn't have a value for the FIRSTNAME contact data field, your email displays the default value, such as Hi Customer, instead of leaving a blank space after Hi.
Default values can be set against any of your contact data fields.
Default values aren’t actually stored against your contacts; for instance, the default value isn't visible when viewing or editing an individual contact. They're only made use of in personalisation.
Default data field values also display in pages or forms where form fields are linked to contact data fields. If a contact has a value for the linked data field, this value displays instead of the default value.
Set a default value for a contact data field
Expand the User menu and go to Settings > Contacts > Contact data fields.
Find the data field you want to edit, then select the Properties icon.
In the Default value box, enter the default value you want to use.
Select SAVE.