My emails are not being delivered to specific domains, what is the cause?

1. Check your email server settings to ensure that it’s configured correctly.
2. Verify that the domain you are trying to send emails to is not blacklisted.
3. Check for blocked IP addresses; if one of yours is blocked, try whitelisting it with the recipient’s email domain.
4. Arrange to have your emails authenticated by the recipient’s server.
5. Change the email address of the user that is sending the emails.