Large email hosts like Yahoo, Gmail, and Hotmail have certain policies that can affect your email delivery rate to their systems. You can find links to these different policies below. Use these guides to craft emails that will have better delivery rates to these systems.
- Yahoo’s Best Practices for senders can be found https://help.yahoo.com/kb/SLN3435.html
- Gmail/ Google Apps Bulk Senders Guidelines https://support.google.com/mail/answer/81126?hl=en
- Microsoft/Live/Hotmail Policies, Practices and Guidelines https://mail.live.com/mail/policies.aspx