How can I connect my Gmail/G-suite alias account with SalesHandy?

Yes, you can connect your Gmail/G-suite account through SMTP. For that, you need to follow below SMTP settings:
Port: 465
Encryption: SSL
Username: Your Gmail primary account email address.
Password: Your Gmail primary account Password.
Refer the below screenshot for your reference:
You can check your primary and alias account details from your Google account settings, refer the below screenshot.
Also, you need to allow less secure apps to your primary account to connect through SMTP. Go to the link to allow less secure apps, refer the below screenshot.