As per the global standards, all emails which are sent to from the internet to any recipient domain are submitted to the MX server of the recipient domain post which the recipient MX server delivers them to users mailbox. Please note that at times due to custom spam filter rules these mails may get stuck in the Spam filters of the recipient MX server and may not get delivered to the mailbox.

In order to identify the exact issue you can do below,

1. Check all the folders of your mailbox including the spam folder. 

2. You can download & share the sent report from the panel with the Mail server admin of the recipient domain to investigate and help you with a resolution to the same issue.