And the really annoying block at Microsoft is back / 2022-06-12

After receiving another mail in the mail exchange that made me note Microsoft outlook.com wasn't blocking my mailserver anymore we're back right in the same spot:

   ----- Transcript of session follows -----
... while talking to outlook-com.olc.protection.outlook.com.:
>>> MAIL From:<***** .at. idefix.net> SIZE=2035 BODY=7BIT
<<< 550 5.7.1 Unfortunately, messages from [45.83.232.134] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [BN8NAM11FT026.eop-nam11.prod.protection.outlook.com]
554 5.0.0 Service unavailable

Aaargh. I thought it wasn't broken anymore. Utterly unreliable stuff at Microsoft.

And I'm back to having to use SMS to explain to very non-technical people why their mail isn't getting through: because they are using outlook.com.

Update 2022-06-13
As a workaround I am now using SMTP2GO to send mail to outlook.com and hotmail.com. SMTP2GO does interesting things (even in a free account) to get the mail delivered and keep their mail 'reputation' in the plus. I hate having to use such a service to get my mail delivered but this is one of those signs that Internet e-mail has been demolished by spammers.