Not all email receivers generate DMARC reports: While most major email providers and receivers support DMARC, some smaller providers may not generate DMARC reports. This means that even if your company sent emails to these providers, you may not receive DMARC reports for those emails.

DMARC reports are generated by email receivers that have implemented DMARC authentication checks on incoming emails. When an email is received, the email receiver checks whether the email has passed or failed DMARC authentication based on the domain owner's DMARC policy. If the email passes DMARC authentication, the email receiver can generate a DMARC report and send it back to the domain owner.

While most major email providers and receivers support DMARC and generate DMARC reports except for Office 365, there are some smaller providers that may not have implemented DMARC authentication checks or do not generate DMARC reports. 

As a result, if your company sends emails to these providers, you may not receive DMARC reports for those emails. This can make it more difficult to get a complete picture of the authentication and delivery status of emails sent from your domain.

To address this issue, some DMARC reporting services can aggregate data from multiple sources to provide a more comprehensive view of your domain's email authentication status. These services can collect DMARC reports from email receivers that do generate reports as well as use other data sources, such as email logs or data from email security services, to provide a more complete view of your domain's email authentication status.