My understanding is that for a dog to qualify as an ESA and therefore be treated as a reasonable accommodation per the ADA rather than a pet, one needs a letter from a mental licensed health professional "prescribing" the particular dog as part of the person's treatment plan. Just having a diagnosis of a mental health issue isn't sufficient to make one's dog an ESA - the letter is necessary. I do believe it's acceptable for landlords to verify the letter is genuine by contacting the doctor who wrote it - it'd only be a HIPAA violation if the doc provided additional personal medical information to the landlord without the patient's permission.
AFAIK the ESA registries are basically scams - registering a dog doesn't make it an ESA per federal law, and dogs that aren't registered can still be ESAs regardless, because there is no official registry recognized by the government, just some private organizations calling themselves registries.
AFAIK the ESA registries are basically scams - registering a dog doesn't make it an ESA per federal law, and dogs that aren't registered can still be ESAs regardless, because there is no official registry recognized by the government, just some private organizations calling themselves registries.