In order for SpamDrain to filter your e-mail the MX records for your domain must be changed to point to SpamDrain's servers. The MX records should look as follows:
10 is the MX preference value. Servers with smaller values will be contacted first by the sender when trying to deliver a message. The preference values don't necessarily have to be 10 but it is important that you use the same value for both of the servers.
NOTE: Please do not add any other servers to your MX records, even if you give them larger preference (which means lower priority). Spammers are known to try the servers with larger values first because they are less likely to run anti-spam software.
To change the MX records for your domain please contact the administrator of your domain's information. This is probably the e-mail hosting provider you are using.
If your e-mail hosting provider is using CPanel to administer your domain you use the MX Entry page to change the MX records. Make sure the Local Mail Exchanger option is checked on this page after you have changed the MX records.