We look after multiple Office 365 tenants for hosted Exchange email.
One tenant in particular has an issue where a lot of inbound and outbound emails are marked as phishing.
The domain passes all DNS checks under the Admin console, and I can't find the domain on any blacklist checks.
SPF: v=spf1 include:spf.protection.outlook.com -all
I investigated enabling DKIM, however unfortunately the domain registrar does not accept underscores in CNAME records.
Can someone please help? The issue is very frustrating for our client.
Thanks!
