Hi William,

There was a piece missing from the other answer that I just updated, I'll post it here as well - this liquid will change the salutation on an email blast for those in your database that don't have a first name in their profile to "Sisters and Brothers" (which you can change to however fits best for how you would like to address your recipients):

{% if recipient.first_name? %}
{{ recipient.first_name }}
{% else %}
Sisters and Brothers
{% endif %}