Changes

# [https://support.google.com/a/answer/178723 Configure SPF records to work with Google Apps] (Google)

# [https://www.digitalocean.com/community/tutorials/how-to-use-an-spf-record-to-prevent-spoofing-improve-e-mail-reliability How to use an SPF record to prevent spoofing and improve email reliabiltiy] (Digital Ocean)