Subject scoring is a common technique used in spam filters to evaluate the likelihood that an email is spam based on its subject line. Here’s how it typically works:
Keyword analysis: The filter checks for spam-related keywords or phrases in the subject line.
Pattern recognition: It looks for patterns commonly used in spam, such as excessive capitalization or special characters.
Length consideration: Very short or excessively long subject lines may be flagged.
Historical data: The filter compares the subject to a database of known spam subjects.
Machine learning: Advanced filters use AI to adapt and improve detection over time.
If the subject line accumulates a high enough score based on these factors, it may trigger a block, resulting in the 550 [SS] error.