on april 6, 2023 i sent fr hotmail emails & on 4/8/23 rejected by multiple recipients email provider

Question

On 4/6/23 i emailed 10-12 people from my hotmail account from the afternoon through to 7pm and they all came back on 4/8 in one swoop at 10am ish with the ie. "Delivery has failed to these recipients or groups: Jordan Moore (@fertilizewithalm.com)Your message wasn't delivered because the recipient's email provider rejected it. Diagnostic information for administrators: Generating server: IA0PR10MB7136.namprd10.prod.outlook.com@fertilizewithalm.com
Remote server returned '550 5.7.520 Message blocked because it contains content identified as spam. AS(4810)' Original message header..." what is wrong with hotmail ? and how do i know if they my email recipients have received the email or not ? how is hotmail / microsoft addressing the