>>> from emails import valid_address

>>> valid_address("pepet@lsi.upc.edu")
True
>>> valid_address("pepet.lsi.upc.edu")
False
>>> valid_address("@pepet.upc.edu")
False
>>> valid_address("t@pepet.upc.edu")
False
>>> valid_address("pe@pepet.upc.edu")
True
>>> valid_address("pepa@pepet@upc.edu")
False