issue with gmail / iphone mail / Mac Mail (desktop)

Hi,
Hoping someone can help me out with this. Sorry it's a bit of a long-winded explanation.

I have an email account (i.e. kmd88@mydomain.com) which is hosted by gmail.
1. I access/download using my Mac and Mail, with pop.gmail.com as server
2. I manually access/download using my iPhone, with pop.gmail.com as server
3. I can access from gmail.com

I have found that if a new message is downloaded first by my iPhone, the same mail does not get downloaded to my Mac. If I log into gmail.com, the message appears as "unread," but it doesn't get downloaded in Mail.

Messages are only into Mac Mail if they have NOT also been downloaded by my iPhone.

I also have a regular gmail account and think I have all the same setups (pop.gmail.com in Mac Mail, and whatever the automatic settings are for gmail on the iPhone). The regular gmail account works properly -- iPhone downloaded messages are still downloaded to my Mac Mail.

Any ideas?

Thanks!