require: https://github.com/themartorana/python-postmark
flask配置文件中设置：
POSTMARK_API_KEY = 'your-key'
POSTMARK_SENDER = 'sender@signature.com'
POSTMARK_TEST_MODE = [True/False]
初始化：
mail = Postmark()
mail.init_app(current_app)
发送：
pm = mail.create_mail(to="to@mail.com", subject="subject", tag="tag", html_body="hello postmark")
pm.send()