PHP mail not showing up at Gmail but shows up at Hotmail and other 3rd party/ISP account

Question

I have 2 sites where mail is sent to two vanity gmail accounts. I\'m using PHP to handle the mail, but the mail is not showing up at gmail (not in spam/junk, it just doesn\

Answer 1

Seems more likely that this is a server configuration issue and not a PHP issue.

As a side note I've found gmail more tolerant than our local system, so I've been able to get messages out to my gmail account, but not my account on the hosting domain.

I don't think Google uses third-party black lists, but they do care about server configuration (does it identify itself correctly, have matching SPF and RDNS records, respond to commands properly). You might try a couple of testing services like this or this.