Content filtering

What it means

Microsoft's documentation uses content filtering as another name for its spam filtering, the proprietary technology that separates junk email from legitimate email after connection filtering has checked the sender's reputation. SpamAssassin's tests on headers and body text, its Bayesian classifier and its checks of link domains against URI blocklists are all forms of content filtering.

Content matters more when reputation gives no clear answer, and links are part of content: domains in the body are checked against lists such as Spamhaus DBL and SURBL, which filter messages by the sites they point to whatever IP sent them.

Google's sender guidelines list content practices to avoid, such as hiding content with HTML and CSS, mixing types of content in one message and links whose destination is unclear.