You may use WinRoute as your SMTP server for outgoing mail. WinRoute uses the SMTP server of your ISP to send email out instead of using MX records. In other words - all outgoing email will be sent through the other mail server that you enter (usually the Mail Server of your ISP). The same rules may be applied to your email clients - WinRoute Mail Server may be their relay SMTP server.
To set the relay SMTP server for outgoing mail:
Authentication
Some ISPs do authentication of email coming through in order to avoid spamming. Then you have to provide your ISP with sufficient information.
1. Go to Mail Server->Advanced tab window
2. Enter desired host name into the Internet host name field. Usually this is the name of the computer connected to the Internet, e.g. host.isp.com.
If a user name and password are required you can only add these settings through the registry. Go to Hkey_Local_Machine/Software/kerio/winroute. Modify MailRelayAuth to '1' and MailRelayUser and MailRelayPassword to reflect the sufficient login information required by your ISP.