Sending, receiving, and organizing email in Outlook.com
Hi, Kirsten. Thank you for coming to the forum. My name is Femi. It is worth noting that this is a user community, and we are all users here, much like yourself. While we strive to assist and share insights, we are not Microsoft directly.
I’m sorry to hear that you are unable to email your friend. As a user, I understand how frustrating that can be. Rest assured I will do my best to provide you with a solution.
According to Xzenor the article in ( https://serverfault.com/questions/998551/understand-if-email-error-is-due-to-sender-or-recipient-server ), The receiving server must have blacklisted your IP.
"The receiving server blocks you. This can have multiple reasons, like:
Your ip or ip-range is being blocked because it's on some abuse list (consumer ip addresses usually are) Reverse lookup on your ip doesn't work your ip is on a blacklist. even more reason But no doubt, the receiving server blocks you. It's just a matter of finding out why."
Note: This is a non-Microsoft site. The page seems to provide accurate and reliable information. Beware of advertisements on the site that may advertise products frequently classified as PUPs (Potentially Unwanted products). Please do thorough research on any product advertised on the site before downloading and installing it.
I hope this helps, let me know if this contradicts what you need. I remain helpful in answering any more of your questions.
Best Regards,
Femi.