When an email comes into our server we run it through vigorous checks to ensure our customer's and server's safety. These steps are detailed below:
- SMTP Connection to our server.
- Greylisting - For more information on this please see KB 1014.
- Email is delivered to our server.
- Our server scans the email for viruses.
- Commtouch - Scans for the likelihood of the message being SPAM.
- Spam filtering steps take place like Reverse DNS, SPF checks, domain keys, Baracuda, SpamCop, content filtering.
- Email is delivered to the user's mailbox.
- A spam weight assigned based on the spam filter's results. Any instructions from content filtering is also applied.
- Checks are run to see if the message was sent from a trusted sender or the same domain name. If this is the case the SPAM weight is set to zero.
- Action is taken based on the user-defined weight and content filtering settings.
Note: This is why content filtering takes effect even if a user is listed as a trusted sender.