Inquiry About Emails Not Being Received in Outlook from a Specific Sender

Hello,

I am contacting you because emails from a specific sender are not being delivered to my Outlook account.

These emails are important for business purposes. I tested delivery using multiple email services, and the messages were successfully received by other mail providers, but not by Outlook. I also added the sender address to my Outlook safe senders / allow list, but the emails are still not being received.

The emails were sent through a legitimate mail service provider, and the sender is considered trustworthy. While the provider may send announcement or promotional emails as part of its service, it is not known to be a spam sender.

The main issue is that Outlook is not delivering emails even from a sender address that I explicitly allowed. Please review and clarify the following:

1. On what basis Outlook is blocking this sender or its sending infrastructure
2. Whether this is caused by Outlook’s filtering or policy enforcement
3. What needs to be done so that these emails can be delivered normally
4. Who should be contacted, and what actions are required from either the sender side or recipient side to resolve this issue

I also contacted the sending provider, and they informed me that Outlook appears to be blocking their mail delivery infrastructure. As a result, emails sent from that provider to Outlook domains seem to be broadly blocked, and many recipients are unable to receive them.

Please let me know the reason for the block and the steps required to resolve it.