From time to time, agents receive emails sent to their remax.net email address with a "From" address of email@example.com, rather than from the original sender. Dmarc@remax.net is a special email address that RE/MAX uses in certain cases to ensure the delivery of emails to your remax.net address. This special case occurs when you receive a message from an email address that happens to use the same email service provider as you (such as Hotmail, Gmail, or AOL). When you Reply to the email it will go to the original sender.
RE/MAX displays the From address firstname.lastname@example.org as a way to get your mail delivered in cooperation with an anti-spam measure called DMARC (Domain-based Message Authentication, Reporting and Conformance) which your email service provider implemented. RE/MAX MainStreet has an article about this: New Anti-Spam Policies Affect Email.
The DMARC anti-spam measure affects millions of email users and billions of email parcels nationwide. RE/MAX and other email service providers use these types of measures to work to ensure that your email is delivered.