We recently added a dedicated IP to our AWS SES pool - 23.249.221.24

We can send email fine to almost all addresses, gmail etc. SPF, DKIM, DMARC records all active and in place.

https://www.mail-tester.com gives us a score of 8.2, with the points lost around lack of text in the email. No issues with blacklists or authentication.

However when sending to an office365 domain, we get a bounce straight away:

Reporting-MTA: dsn; d221-24.smtp-out.amazonses.com

Action: failed
Final-Recipient: rfc822; jack@365domainhere.com
Diagnostic-Code: smtp; 550 5.7.606 Access denied, banned sending IP [23.249.221.24]. To request removal from this list please visit https://sender.office.com/ and follow the directions. For more information please go to  http://go.microsoft.com/fwlink/?LinkID=526655 AS(1430) [ME1AUS01FT003.eop-AUS01.prod.protection.outlook.com]
Status: 5.7.606

I followed the instructions at sender.office.com over 12 hours ago and confirmed we're not blacklisted there.

I've opened a ticket with 365 support and they have confirmed there is no blacklist issues in place.

Emails sent to an outlook.co.nz address are delivered but appear in the spam folder, no matter how many times I mark them as not junk.

Any other ideas on how to resolve this? Is it just a longer waiting game?