Amazon pinpoint emails (with using SES service) have been recognised as spam email in Microsoft 365 email account

Yes, the issue of emails sent from Pinpoint service using AWS SES being recognized as spam in Microsoft 365 Outlook could be due to sender reputation issues. If your sender reputation is poor, it can affect your email deliverability and cause your emails to land in the spam folder. Applying dedicated IPs in AWS SES can help improve your sender reputation and increase the chances of successfully sending emails without them being identified as spam. Other ways to tackle not being recognized as spam include following email best practices such as using a clear subject line, avoiding trigger words, and sending emails to engaged recipients who have opted-in to receive your emails.