[~The_Sultan~]

בקשר לזה, תראה מה כתוב שם:

if your mail is failing (returns false) be aware that many servers are configured to kill mail going out with a bcc or cc header.

The ideal workaround is to use the smtp functions which servers allow because of its better audit trail. Alternatively call the mail function several times.

I've just spent about four hours trying to work out what I was doing wrong!!