Miscrosoft has recently decided to embrace DMARC more explicitly, much like their email brethren, Yahoo, AOL, and Gmail. You may have started seeing bounce messages with the following reasons:

Hotmail / Outlook / MSN / Live:

550 5.7.1 The messages violates the DMARC policy of domain.tld (1b6c35a4-2c11-11e6-ab23-549f350a57e2)

550 5.2.0 54Qa1t0144ZKE95014QaMR Message rejected due to DMARC. Please see http://postmaster.comcast.net/smtp-error-codes.php#DM000001

550 5.2.0 54QF1t03z3oQ44H014QGZ3 Message rejected due to DMARC.

This is because Microsoft will no longer be accepting messages where the From domain is a Microsoft domain address and the message originates from a non-approved Microsoft mail domain server/service. This is a security measure they have implemented to help reduce potential address spoofing of their mail domains.

What this means: As of June, 2016, you can no longer send with the From address being anything from a Microsoft address when sending to a domain that checks DMARC before accepting mail.

What you can do: You will need to change the From address you use in emails to a non-Microsoft address. We recommend using one at your own mail domain, or one you control that is legitimate. You can then set the Reply-To field to be the original Microsoft address that previously was used in the From field.

What about these messages, are they lost? : Yes, any send with this bounce message is discarded and tracked as a Block. You will need to adjust your From address field settings, and then try resending from your side.

For more extended reading, check out check out this article on the DMARC changes, as well as our DMARC Classroom article.