Emails I send as a cc or bcc NEVER GO THROUGH TO THA RECEIVER !!

Emails I send as a cc or bcc NEVER GO THROUGH TO THA RECEIVER !!

every time i send a cc or bcc copy of an email to anyone when I’m using my zohomail.com email - no one ever gets the cc of bcc copy if the email: why???? And i triple check that the email addresses are correct; then i get back an email message  (EVERYTIME) that it did not go through. And I am only sending about 2-3 persons max that I cc. Why is this? Do I need to sign up to be a paying subscriber so this doesn’t happen?  I will if necessary if that fixes the issue. It’s extremely frustrating! Thanks