Last week, had trouble getting email to a contact. Turns out they were running a spam filter from CIsco...
"Your mail server has a low reputation and is based off-shore he wrote. Our spam filter flagged it." He included a link to Cisco's reputation Lookup site to substantiate his statement. Baffled, visited the site to take a look.
The site is beautifully styled in delicate yet unreadable grey font on a black background. Perhaps fittingly so. If you enter gmail.com in the search box, it shows the servers to have a poor reputation score of 2.58 out of 10, located in "Null, India" and a few other real and imaginary locations in rural India. (Searching Google Maps for "Null, India" comes up empty.) Being GSuite customers, Google hosts our corporate email. Those emails did not get through, and personal gmail met a similar fate. Not surprising, if the geographic analysis is any indicator. Likewise, Talos claims "outlook.com" has a low reputation score of 1.55/10 and is based in Vienna, Austria. Strange though, since Cisco claims "The Talos Email and Web Traffic Reputation Center (formerly known as SenderBase) is the world’s most comprehensive real-time threat detection network." In short, lovely domain name, great site styling, but antiquated technology that dismisses billions of legitimate users as spammers.
Although Google and Office365 have stringent anti-spam enforcement, legacy security technologies that rely on basic attributes like server IP address are unable to handle globally distributed cloud services.