Looking to group my customers together based on their interests and send them email news on those topics.

I found a couple options for this but not sure which is best, or maybe there is another way I haven't found yet.

• Importing the contacts via csv and using the mass mailing option. It must be possible to apply to them a custom field for their interests but this may not be manageable by the customer themselves.
• Using messaging groups and assigning customers to them. From what I understand this could allow customers to follow or unfollow public groups (or newsletters) from the portal. This seems like a better route but not sure if the portal would allow new customers to sign up without being added by an employee.