If you face any problem to connect IMAP of Gmail, please check this:

1. Go to Google Account and navigate Security tab.
2. Enable 2-Step Verification from Signing in to Google section.
3. After this, there will be a new section called App passwords in Signing in to Google section. Click on that.
4. From Select app dropdown, select Other (Custom name).
5. Input any name like RISE and click on GENERATE button.
6. You'll get the password with yellow badge on a popup. Use this password in the mailbox setting instead of your main password.