I have spent close to 5 hours trying to get e-mail and am just about to give up on Mantis.
I have not having any success using either gmail or my hosting email service (dreamhost).
I am in a different problem. It works fine with gmail smtp until I changed password in gmail account. I fired up tcpview and looked at its connection activity. It seems it was reject from smtp server. It sends one packet (5X bytes data) and disconnects. Apache tries three times and gives up. I tried reset my gmail password to the previous one and did not work either. Any suggestion?
It wouldbe good if you want to solve your issue still to use a regular email client like Thunderbird and make very sure you can at least get and send email in that program. use the EXACT same login username and password and settings as you use in this email program...