import re

email = "john@invoice.telenet.be"

m = re.search(r'@([^@]+)$', email)
if m:
    # We have a match
    domain = m.group(0)
    domain_parts = domain.split('.')
    # the penultimate part: 'telnet'
    print(domain_parts[-2])
    # the last 2 parts: telnet.be
    print('.'.join(domain_parts[-2:]))