Libra Esva introduced, in version 4.x, a graymailing (advertising) plugin which can be enabled or disabled in System->Content Analysis->Anti-Spam Settings->Antispam General Settings. This plugin blocks only advertising messages and is a no-brainer solution to the problem.
In version version 3.x the administrator can create custom spam rules to mitigate the advertising email issue by blocking specific senders, here are some examples:
t.contactlab.it (regex: /t\.contactlab\.it/i )
amazon (regex /amazon/i )
booking.com (regex /booking\.com/i )
groupon (regex: /groupon/ )
badoo (regex: /badoo/i )
mailup con i domini .rxx.it (regex: /\.r\d\d\.it/i )
facebookmail.com (regex: /facebookmail\.com/i )
bounce.linkedin.com (regex: /bounce\.linkedin\.com/i )
mailjet.com (regex: /mailjet\.com/i )
bloomberg.net (regex: /bloomberg\.net/i )
mega-offerta.it (regex: /mega-offerta\.it/i )
expedia ( regex: /expedia\./i )
groupalia ( regex: /groupalia/i )
HI-Sender (regex: /emailsp\.net/i )
pazzixsconti (regex: /pazzixsconti\.it/i)
scontissimi.me (regex: /scontissimi\.me/i)
bounce.n.dalani.it (regex: /bounce\.n\.dalani\.it/i)
Vivigratis (regex: /vivigratis\.com/i)
System-> Spam And Quarantine Settings -> Custom Rule
Remeber: Apply Settings
More generally freezes many advertising emails (although it may cause blockage of any newsletter desired) the following rule:
bounce (regex: /bounce/i)