Recently our mail server's reputation has been down rated by Hotmail, according to postmaster/live SNDS-service (from green to yellow and a single day in red). Therefore, me and my colleagues are now running a check of everything send from the mail server to see if all is in order: DKIM, SPF, DMARC, rDNS and so forth. Our mail server is not new, and have over the last 1,5 years had a fine reputation at Hotmail, and is still having a fine score by senderscore.org, ndswl.org and Gmail.
The mail server is sending e-mails on behalf of somewhat 20 different companies, which are using our customer relation system, as a part of our service. As I am now checking up on all the different companies’ domain reputation to figure out what is going on at Hotmail, I can see some of the domains are suffering.
Even though the SPFs, DKIMs and DMARCs mostly are set correctly for our specific mail server in the domains, some of the companies' DNS records are not set right for other mail servers, they use in their communication. (I believe it is not spammers who are abusing our customers’ domains, but probably a lack of attention to the importance of setting up the relevant DNS-records and certificates, by our customers).
Now my question is: Can the lower reputation of some of the companies' domains hurt our mail server's IP-reputation? - Taken that the DKIMs, SPFs, DMARCs and so on are set up correctly at the domains for our mail server? Generally, can a lower domain reputation hurt an IP reputation? - And does Hotmail use this in the calculation of an IP's reputation?
I sincerely hope not, since it will be a major issue to fix and very up the hill, with a dozen of companies' domains and different levels of attention to email delivery by the customers. But after all it is better to know, and then take some action to set it all up in a different way.
Thanks for reading.