Postie works well with Gmail (and Google apps for business), however, there are a few things that can get in the way.
First make sure your hosting company allows access to external mail servers. GoDaddy notably does not allow this. If you are hosting with GoDaddy there is no way to use Gmail, you must use the GoDaddy email server.
Second make sure you have enabled POP3 (or IMAP) access to your Gmail account. Go to the Forwarding and POP/IMAP tab in your Gmail settings and click the Enable POP for all mail radio button. See also the Gmail help page.
Finally set you settings to:
- Protocol: pop3-ssl
- Use Transport Layer Security: no
- Server: pop.gmail.com
- Port: 995
- Userid: your full email address
- Password: your password
Note that if POP3-SSL is not a choice in the protocol combobox you either need to enable the PHP extension php-imap or choose a different mail server. Gmail will not work with POP3.