Google allows you to send email through the Gmail mail servers, even for custom Google Apps domains!
Enable POP
First, enable POP for the email accounts you want to send email through
- http://mail.your-domain.com/
- Click "Settings"
- Click "Forwarding and POP/IMAP"
- Click "Enable POP"
Send Email
To send email, use
- Server: smtp.gmail.com
- Port: 587
- Domain: (your Google Apps domain)
- Username: [email protected]
- Password: your-password
- Authentication: plain
- Encryption: TLS