Вместо smtplib.SMTP попробуй так:
import smtplib
SMTP_SERVER = "mail.hosting.reg.ru"
SMTP_PORT = 465
SMTP_USERNAME = "***@**.ru"
SMTP_PASSWORD = "***"
with smtplib.SMTP_SSL(SMTP_SERVER, SMTP_PORT) as server:
server.login(SMTP_USERNAME, SMTP_PASSWORD)
print("Good")