Are you in search of the best center to get the ESA letter online for your emotional support animal? You need an emotional support animal to get over the stress. Emotional support animals would help treat your mental health condition. You need to get an ESA letter which is a prescription for an ESA. The letter must come from a licensed mental health professional. Your letter must be on your therapist's official letterhead. Must include your therapist's license details, issue date, and state.