1. Gmail has a feature called Send Mail As. This feature allows the user to send email from another domain through their Gmail account. From their help page:
================================================ "If you own another email address, you can send mail as that address. For example:
Yahoo, Outlook, or other non-Gmail address Your work, school, or business domain or alias, like @yourschool.edu or youralias@gmail.com Another Gmail address Tip: You can send emails from up to 99 different email addresses." ================================================
2. I have happily been using it for sending and replying to my Hotmail/Outlook account for over a decade.
3. Suddenly Gmail is rejecting sending to these Hotmail addresses via alias. The error message reads:
550 5.7.26 This mail is unauthenticated, which poses a security risk to the sender and Gmail users, and has been blocked. The sender must authenticate with at least one of SPF or DKIM. For this message, DKIM checks did not pass and SPF check for [hotmail.com] did not pass with ip: 209.85.220.41.
4. On checking it appears that:
a) That IP belongs to Google. So Google is blocking its own feature b) The reason may be that Spamcop (and only Spamcop) has blacklisted that IP.
5. The bottom line is, a service which Google offers for free to its users for convenience is now broken (due to Google inaction?).
6. I'm not going to go down the rabbit hole of wondering whether this has anything to do with a general Google/Microsoft issue.
7. Yes I know I'm the product and I really should just stop using Gmail. But hey...