Sending emails with Gmail
Visit https://mail.google.com/mail/u/0/#settings/accounts to access your Gmail "Send mail as" settings
Once there, click "Add another email address" and a popup like the one below will show up:
Name: Enter a name you'd like people to see when they receive an email. If this is a "email@example.com" email, you might want to name it "Project Support"
Email address: The email inbox you added in Sidemail, for example "firstname.lastname@example.org"
Then click "Next Step" and you'll see:
Within Sidemail (after you create your inbox), we'll show you the username and password required for sending emails.
On the account page https://mail.google.com/mail/u/0/#settings/accounts, we recommend using the following setting: