Please see this answer...
Sending Email from Visual Basic
If you still can't send the email....
Have you enabled POP or IMAP in Gmail?
Sign in to the Gmail web interface.Open the 'Forwarding and POP/IMAP' tab on your 'Settings' page, and configure IMAP or POP. After enabling this in Gmail, make sure you click 'Save Changes' so Gmail can communicate with your mail client.
If you have 2 step verification..
Get an Application-Specific Password
Google will automatically generate a password that you will need only once, when you set up Google Mail on your mobile device or email software. You can easily generate a password for each device or email software you want to use.
Step 1:
At the bottom of the 2-step verification screen, next to Application-specific passwords, click Manage application-specific passwords. The Authorized Access to your Google Account screen will open.
Step 2:
On the Authorized Access to your Google Account screen, in the Name field, type in a name to help you remember what application you are using to access your account and click Generate password. You will then see a password which you will use to configure your mobile device or email software. Keep this screen open until you are ready to enter the password (see part 4, below). The password creation with the device name will show at the bottom. When you are done using the password, click Done.
Step 3:
To set up a password for another device or email software, simply type in the name of it in the Name field and click Generate password. You will receive another password.
See more here...
http://www.oit.umass.edu/support/google-apps/configure-google-mail-email-software-mobile-devices
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