Upcoming: DMARC compliance enforcement

Intended audience

Miami communicators who use email-sending services (e.g., MailChimp, Emma, Constant Contact) to message users outside the Miami domain.

Key takeaway

Miami senders who use these services to send more than 5,000 emails per day to users outside the Miami domain may start to see rejection messages starting Feb. 1. 

Do you ever send more than 5,000 emails per day to recipients outside the Miami domain (i.e., to or addresses)? If so, this notice is for you!

Email security is a priority for Miami and the IT teams that support the service, and Miami has been working on making sure all of our systems are compliant with Domain-based Message Authentication, Reporting, and Conformance (DMARC) requirements. Over the last year, we have made a lot of progress in that regard. Now, Google and Yahoo are taking part of that burden off our shoulders, so to speak, with some new rules they will begin to enforce in February.

Starting February 1, 2024, Google and Yahoo will begin to enforce some security policies in an effort to improve the default security of email correspondence. This policy is referred to as DMARC. What DMARC does is help protect against email spoofing (i.e., when a cybercriminal masquerades as a legitimate sender) by authenticating with and aligning distinct security mechanisms.

After Feb. 1, emails sent to Gmail or Yahoo addresses will be subject to this DMARC policy. What that means is that if an email sender is not DMARC compliant and they send bulk messages (more than 5,000 in one day) to or email addresses, they may receive a notice that their message has not been delivered to the intended recipients.

This will primarily impact mail-sending services like Emma, Constant Contact, MailChimp, Slate, and other bulk messaging services. Miami users will not need to worry about sending mail from their own email accounts – DMARC is primarily looking for services that are “spoofing” or impersonating a Miami email address to send these notes.

Please note: This will not impact messages that Miami users send to Miami recipients (i.e., “in-house” communication). So if you send messages to someone with an email address, you’re good to go! 

If you or your office has access to an email-sending service and regularly sends bulk email to addresses outside the Miami domain (e.g., and addresses), you may start to see rejection messages starting Feb. 1. If you receive those messages, please reach out to IT Help at 513-529-7900 or Our email security team will work with you to ensure the messages get delivered.