I know you hate microsoft BOAC but it's not really their fault if people don't bother to take the trouble to read the help pages or view one of the many 'How To' videos that MS produce about a product, it's all about education.
- wrong! I am a M4 user. What I hate is the whizzy bang 'ideas' these kids come up with which intrude into innocent users' innocent use. If you read my links you will see that I did everything required, including SPFs in 'consultation' with M$ Hotmail 'help' who eventually stopped answering when they couldn't fix it, and still emails were being blocked as 'spam'. "See you at 1500". Nasty spam, you'll agree?
This came from my host:
"As the error is occurring on their servers, our logs will not contain anything useful. They simply show our email server attempting to send the email to hotmail, and getting that error message in response.
Like most of the large free email providers, hotmail will often block legitimate emails as part of their "anti-spam". If the recipient uses email for anything important,
a reliable email provider should be used who will not block emails without the users permission. Attempting to get any information from hotmail about why it was blocked will prove futile, the same as with most of the other big free providers."
My bold and excellent advice. Trouble is, how to persuade your contacts? Plus, of course, the other "big free providers" are not so paranoid.