During a CSV import to a list, will checking "update existing contacts" and "import as active" add contacts as active to the list?

This will update and add existing contacts to the list unless the contact unsubscribed themselves from ALL lists or that specific list in the past.

Other things to note:

• If the contact is active on other lists, they will be added
• If the contact was not on any lists but is an active contact, they will be added
• If the contact unsubscribed from any list, they will not be imported via .csv to a new list even if the box is marked "update existing contacts"