(the sender is smtp.gmail.com - port 587 - no ssl - with authentication)
For gmail, you need SSL
I posted this previously
https://www.nopcommerce.com/boards/t/10565/nopcommerce-v200-beta-released.aspx?p=9
But I'll repeat it here because the end of that thread got weird (not related issues).
(and I'll also correct "User: ...gmail.com", because that has to be the gmail account that is logged into)
These are gmail settings I use
Email address [email protected]
Email display name: DisplayName
Host: smtp.gmail.com
Port: 587
User: [email protected]
Password: <password>
SSL: <checked>
Use default credentials:<NOT checked>
Be sure you SAVE your changes before you click the Send Test Email button.