It's an industry standard best practice to encourage subscribers to add your from address to their safe sender/contact list. The best time to do this is in a welcome message. Subscribers are most likely to respond when they first sign up because they are the most interested at that moment. Therefore, if a subscriber has just signed up to receive email from you, it’s a good idea to request that they “whitelist” your from address. This can help improve your sender reputation with their ISP as well as increase future deliverability and engagement rates.
Here are some examples that you can add to your welcome messages. Please replace [FROM ADDRESS] with your from address email.
"For best delivery, please add [FROM ADDRESS] to your address book or Safe Senders List."
"To ensure delivery to your inbox, please add [FROM ADDRESS] to your address book or Safe Senders List."
"Please add [FROM ADDRESS] to your Contacts List in order to ensure the delivery of our communications."
"To keep receiving emails from us, please add us to your address book."
You can also send your subscribers detailed instructions for how to save your from address to their safe sender list (also called whitelisting). This can help make the process simple and easy.