Internet
Strumenti per controllo DNS, SPF, MX, SPAM
https://www.spfwizard.net/https://mxtoolbox.com/SuperTool.aspxhttps://practical365.com/exchange-server/a-sender-policy-framework-spf-primer-for-exchange-administrators/https://mxtoolbox.com/Public/Tools/EmailHeaders.aspxhttps://www.mail-tester.com/