One of the great psychological motivators is the feeling of belonging to a club. A feeling of gaining exclusive access to something will help people give up something, in this case, their contact information, an email address. Instead of “join our mailing list,” use language like “Gain Exclusive Access.” Instead of “signup,” use “register.” Your email newsletter has so much value and resource in it that you don’t have to beg people to join, instead, they should have a feeling that they want to register to receive it.
Create opportunities for exclusive content for your newsletter. Feature a story about your donation recipients available no where else, or highlight an exclusive opportunity for supporters to join you for an event. Creating exclusive content will help generate demand for your product.