Grazie per il suggerimento.
Ho provato (DNSChecker) ma mi sembra tutto ok.
(xxxxxxx al posto del nome dominio..)
MX Records
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xxxxx.mail.protection.outlook.com.
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>>> Mx Record => xxxxx.mail.protection.outlook.com.
>>> IP => xxxxxxxx
>>> Status => Success
>>> Test duration(ms) => 74
>>> AS Number => AS8075
>>> Organization => Microsoft Corporation
>>> Domain => microsoft.com
>>> Country => Netherlands
>>> Abuse Contact => Network: 104.40.0.0/13
Name: Microsoft Abuse Contact
Email: xyz@abc.ch
Phone: +1-425-882-8080
Address: US, WA, Redmond, One Microsoft Way, 98052
Country: US