Emails from users with Outlook.com country domains may not be reaching Gmail addresses but fear not - Microsoft has a workaround.

The problem, where users send email to a Gmail account and receive a terse response from Google that their message was blocked, has been acknowledged by Microsoft and a temporary solution issued:

"Add an Outlook.com alias to your account and send email to Gmail users using that alias."

It's a less-than-ideal workaround and could trip up other filters set up by the recipient. It should, however, deal with the particular issue that is causing Google's servers to spit out the response:

"Remote server returned message detected as spam -> 550 5.7.1 [[ IPAddress]] Gmail has detected that this message is likely suspicious due to the very low reputation of the sending domain. To best protect our users from spam, the message has been blocked."

Microsoft did not elaborate on the cause, only that affected users would have to use the only remedy it has available until the Outlook team addresses the issue. Google, however, provided a little more detail in a support document.

It says: "If we detect that a message has a strong likelihood of being spam, we'll block the message from being sent to Gmail."

"A message might be blocked if it contains suspicious-looking or spammy text or if the sending IP has had a history of sending unsolicited messages."

Google tightened up its guidelines for email senders in February 2024 and, from April 2024, warned that it would be blocking non-compliant traffic.

"Rejection," said the search giant, "will be gradual."

This is not Microsoft's first rodeo when it comes to email delivery problems. In March 2024, Exchange Online ran afoul of anti-spam measures at AOL and Yahoo after spam-tracking services placed some of the company's IP addresses on the naughty step.

We asked Microsoft when it expects the problem to be fully resolved. We will update this piece should the company provide an estimate. ®

https://www.theregister.com//2024/04/03/outlookcom_blocked_by_gmail/