1. Login to your Siteground account
  2. Under the My Accounts tab, click on the Information & Settings tab
  3. Find and copy the FTP Hostname
  4. Login to your Gmail account
  5. Click the Gear
  6. Settings
  7. Accounts and Import tab
  8. Send mail as: Add another email address you own
  9. Uncheck “Treat as an alias.”
  10. SMTP Server: the FTP Hostname you copied from Siteground
  11. Port 465
  12. Username: your full email address.  Example: name@yourdomain.com
  13. Secured connection using SSL
  14. Add Account
  15. Done!