If a recipient has marked one of your emails as unsolicited mail or as spam, the recipient’s mail server can move your email to the spam folder or it can be rejected. In such cases, you need to apply a delisting for your domain name from the respective provider.
Gmail:
https://support.google.com/mail/contact/bulk_send_new?rd=1
Office365:
https://sender.office.com/
Hotmail:
https://support.microsoft.com/en-us/getsupport?oaspworkflow=start_1.0.0.0&wfname=capsub&productkey=edfsmsbl3&locale=en-us&ccsid=636165331655894043
Apple:
https://support.apple.com/en-us/HT204137
Yahoo:
https://help.yahoo.com/kb/postmaster?redirect=true