Can't send mail with PHP mail function

Question

There are two domains available in my Google Workspace Account. There Gmail service is activated as well.

1. metavsummit.com (Primary Domain)
2. cryptovsummit.com (Secondary Domain)

I've tried using simple mail("info@cryptovsummit.com","Testing","Testing Message") function. But somehow I can't receive email to the mentioned email info@cryptovsummit.

Infact I can send & receive email from info@cryptovsummit but I can't receive mail if I use mail() function of PHP.