I am setting up DMARC right now. I just moved to Office 365 and I was using the none setting, to just report on what legitimate services might be sending out. Freshdesk was the only one that I found and after spending 2 weeks with their support fixing their DKIM record configurations, I enabled quarantine on DMARC. Coincidentally, this is pretty much the exact time when Freshdesk had at least one of their IP addresses get blacklisted for sending mail.
All of our notification messages were getting quarantined by office 365 and I thought it was an issue with DMARC. Nope. What a PITA. I switched the DMARC to none again and that didn't work and finally found out from Freshdesk that they had been blacklisted.
I ended up having to create a mail flow rule to bypass spam filtering if the sender was a certain email address and the return path was several domains with freshdesk in them. That only solved our problem of quarantined notifications. Our customers are still affected. Freshdesk said that they had resolved it by getting the IP removed, but whenever I disable the mailflow rule, they start getting quarantined again.
#badtiming