spam/SPFについて、ここに記述してください。

1. spam 対策

https://www.ipa.go.jp/security/topics/20120523_spf.html

DNS/SPF

http://salt.iajapan.org/wpmu/anti_spam/admin/operation/information/spf_i01/

2. SPF to IP

https://pypi.org/project/SPF2IP/

3. netaddr

https://pypi.org/project/netaddr/

https://netaddr.readthedocs.io/en/latest/