Explanation
One of the best practices to increase email subscribers is to collect emails at offline activities, including in stores1. This way, NTO can capture the interest of potential customers who are already engaged with their brand and products. NTO can also offer incentives, such as discounts or freebies, to encourage customers to sign up for their email list. By collecting emails at offline activities, NTO can build a permission-based and relevant email list that can improve their deliverability and engagement rates.
Sending an SMS to NTO's entire customer database with a link to subscribe is not a good practice, as it may violate the consent and privacy laws of different countries2. Moreover, sending an SMS to customers who have not opted in for SMS communication may annoy them and damage NTO's reputation. NTO should only send SMS messages to customers who have explicitly agreed to receive them and provide them with an easy way to opt out.
Sending an email to NTO's entire customer database asking for referrals is also not a good practice, as it may result in spam complaints and unsubscribes3. Asking for referrals should be done in a targeted and personalized way, based on the customer's behavior and preferences. NTO should also provide incentives and clear instructions for customers who want to refer their friends and family to NTO's email list. References := 1: Optimizing Marketing Cloud: Best Practices for Managing Inactive Accounts - Salesforce 2: How You Can Keep Email Subscribers Engaged | Salesforce 3: Email Marketing Best Practices - Salesforce.com