Outlook.com and Hotmail have been quietly rejecting emails from domains without a DMARC (Domain-based Message Authentication, Reporting, and Conformance) record since November 5, affecting even small senders. The rejection results in a bounce message, and the issue often arises despite the domain having working SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) records. To resolve the issue, adding a single DNS record for DMARC can fix the problem, which ties the SPF and DKIM records to the "From" address, allowing emails to be delivered to Outlook.com, Hotmail, and other Microsoft consumer mail services.