All email being delivered to SFU recipients is passed through a program that gives the message a rating that indicates how likely the message is SPAM (unsolicited email). It sometimes happens that a legitimate email is marked as SPAM even though it isn't.
You can ensure that email from trusted senders is not marked as SPAM by adding them to your whitelist. Any email that contains an entry from your whitelist in either the From: or To: header will be sent to your system inbox. An X-Whitelisted: header will be added to the message so that you know which whitelist entry allowed the message through.
There are three types of entry that you can add to your whitelist.
For more advanced control of your whitelist, see the section on
including regular expression patterns in the entries