Microsoft:

1. Set up on https://sendersupport.olc.protection.outlook.com/snds/

2. Read everything at https://sendersupport.olc.protection.outlook.com/pm/

3. Make sure everything is fixed, then use the link to the form hidden under Troubleshooting > "Sender services, tools, and issue submission" (the link's label is "here") to contact support. Make sure all fields are provided, including a website. It may take a few days to get a response. You may have to try multiple times until someone actually helps you.

Google:

Pray