Looks like you are sending your e-mail through the ip-address that is in bad reputation list.
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IP Query Result:
IP Address: 216.52.72.102
Risk Level: High Risk
Description: This IP address is used for sending Spam on a regular basis
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That ip-address belongs to the Zoho network. So, your e-mails travels trough the bad reputation network. You could forward this information to your IT-support.
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This is the answer I got when asking why a server of my client blocks my emails. Anything you can do about this?
Jari