Microsoft starts blocking improperly configured bulk mailers

[thewayne]

If a mailer is trying to send more than 5,000 emails a day to Outlook.com, Hotmail.com, or Live.com email addresses, and the server is not configured to standards, Microsoft is going to block the emails from going through their networks with an error message. Yahoo and Gmail have been doing this for some time.

Specifically, "... (the) SPF record must clearly identify which IPs can send on your domain’s behalf. DKIM must sign the message with a valid key. And DMARC needs to be published, with alignment to either SPF or DKIM. Preferably both. Without all three in place, Microsoft will silence you."

This will make it harder for fly-by-night spammers to get messages through as they often do not have top-shelf IT people supporting them. It will also cause problems for legitimate mass mailers who use third-party email providers who also do not have top-shelf IT people who may be a little soft on their mail server configuration.

But this is the price paid because scammers are determined to make sure that we cannot have nice things.

https://techcommunity.microsoft.com/blog/microsoftdefenderforoffice365blog/strengthening-email-ecosystem-outlook%e2%80%99s-new-requirements-for-high%e2%80%90volume-senders/4399730

https://betanews.com/2025/05/05/microsoft-email-blocks-start-may-2025/

https://it.slashdot.org/story/25/05/05/1817247/microsoft-cracks-down-on-bulk-email-with-strict-new-outlook-rules

Comments

[ranunculus]

Yeah, this includes my website address that is hosted on Donald's brother's computer. People can email me, but I have to email back on a different email or it bounces. One of these days I have to find someone to fix the website and at that time I'll see about changing hosts. Sigh.

[silveradept]

Yep. The worst thing about having built a system on top of things that are supposed to be trustworthy is that there are people who think that taking advantage of trust for money (or crime) is a good thing and they should do it.