>>> text1 = 'id1:manager.500@domain.ru,id2:manager.501@domain.ru'
>>> text1 = text1.split(',')
>>> text1 = [item.split(':') for item in text1]
>>> text1 = dict((k,v) for (k,v) in text1)
>>> print(text1)
{'id2': 'manager.501@domain.ru', 'id1': 'manager.500@domain.ru'}