What is the issue here?
The main issue is the absence of diagnostic feedback.
Another issue is that the question's title is about SMTP but the body is about POP3/IMAP. These are different protocols used for different purposes. An SMTP client cannot communicate witha POP3 or IMAP service and vice versa. Most clients use SMTP for sending mail and POP3/IMAP for collecting received email.
Use tcpdump or wireshark to watch OSQA attempting to collect email. Look for errors being reported by Gmail or connection failures.
Use tcpdump or wireshark to watch a normal POP3 or IMAP client communicating with your Gmail account, compare with what OSQA is doing.