If setting up the gmail alias doesn’t work, your webmail’s credentials might be different than our’s from this tutorial. Start by opening up your webmail home at mydomain.com/webmail
Then scroll down to the bottom and select Configure Mail Client.
Now go back to your gmail, go to the settings, and click Add an email address. Use the SSL credentials on the left to setup your account.
If that doesn’t work, reach out to support and we’ll be happy to help troubleshoot further.